referring to fig1 and fig1 a , a fastening device includes a first casing 10 , an inner holding part 20 , a waterproof screw annulus 30 , a positioning nut 40 , a connecting annulus 50 , a second casing 60 , an inner buckled nut 70 , a resilient washer 80 and a constricting gasket 90 . the first casing 10 defines a through hole 11 . a slope 12 and an inner thread section 13 are formed therein . the inner holding part 20 includes a collar 22 and a clamp 21 . the inner holding part 20 locates at an inner side of the waterproof screw annulus 30 for clamping the cable l . the waterproof screw annulus 30 is a hollow column . the waterproof screw annulus 30 includes a first thread section 31 , a second thread section 32 , a block 33 and a slanted portion 34 . the slanted portion 34 locates at an inner side of the first thread section 31 . the block 33 is positioned between the first thread section 31 and the second thread section 32 . the first thread section 31 can engage with the inner thread section 13 of the first casing 10 . the positioning nut 40 includes an inner thread section 41 , a positioning slot 43 , and at least one waterproof flange 42 ( referring to fig3 and fig3 a ). the waterproof flange is configured for an annular shape , and positioned at an axial surface of the positioning nut 40 . the positioning slot 43 is annular wedge - shaped slot . the connecting annulus 50 is a hollow column . the connecting annulus 50 has a positioning annular flange 51 at one end thereof , an outer thread section 52 at the other end thereof , and an inner thread section 53 therein . the positioning annular flange 51 has a taper - shaped section for facilitating engaging with the positioning slot 43 of the positioning nut 40 . the positioning slot 43 mates with the positioning annular flange 51 to form a sealed waterproof assembly , and the inner thread section 53 and the inner thread section 41 of the positioning nut 40 engage with the second thread section 32 of the waterproof annulus 30 tightly . the second casing 60 defines a through hole 61 therein , and has a slanted portion 62 and an inner thread section 63 . the inner buckled nut 70 is a hollow column . the inner buckled nut 70 has an inner wall 701 . one end of the inner wall 701 extends out to form an outer wall 702 which parallels to the inner wall 701 . a slot 71 is defined between the inner wall 701 and the outer wall 702 for receiving a wave hose . the inner wall 701 is resilient . at least one positioning tab 711 is formed at one side of the inner wall 701 . the positioning tab 711 is used for resiliently retaining the wave hose from an inner side thereof . the resilient washer 80 has an inner wave surface 801 , and a slanted portion 802 . the resilient washer 80 is positioned inside the second casing 60 , and sandwiched between the second casing 60 and one end of the inner buckled nut 70 for engaging with the wave hose s . further , a constricting gasket 90 is provided between the connecting annulus 50 and the inner buckled nut 70 . the constricting gasket 90 has a slanted portion 901 . the constricting gasket 90 is used for retaining one end of the cable and provides waterproofness . the block 33 of the waterproof screw annulus 30 has a washer attached thereon . the washer 301 has at least one waterproof flange 3011 on an axial surface formed thereon for preventing seeping in the vapor directly . referring also to fig1 , a board d is set between the waterproof screw 30 and the positioning annulus 40 . the board d may be l - shaped or t - shaped ( not shown in drawings ). the board d has an insert hole dl defined therein for receiving the second thread section 32 of the waterproof screw annulus 30 . the waterproof flange 42 of the positioning nut 40 contacts with the board d , and is forced to attach thereto to form a waterproof layer with proper deformation . the fastening device can be adjusted to any proper angles for preventing the connector of the cable c from breaking off by the stress . moreover , the washer 301 is set between the block 33 of the waterproof screw annulus 30 and the board d . the at least one waterproof flange 3011 of the waterproof screw annulus 30 not only prevent seeping water from the insert hole d 1 , but also enhance the attachment between the fastening device and the board d . furthermore , a positioning annulus 54 is set inside the connecting annulus 50 . the positioning annulus 54 is a hollow column . the positioning annulus 54 has larger diameter at one end thereof for abutting onto the inner side of the connecting annulus 50 , so the positioning annulus 54 can receive a frail cable , such as a fiber cable , therethrough , and hold the fiber cable firmly for preventing from breaking off . the material of the positioning annulus 54 can select from resilient rubber or plastic . referring also to fig2 b , the cable l is inserted into the through hole 11 of the first casing 10 , and goes through the inner holding part 20 , the waterproof screw annulus 30 , the positioning nut 40 , the connecting annulus 50 , and the constricting gasket 90 , and passes through the inner buckled nut 70 and the resilient washer 80 , and out of the through hole 61 of the second casing by sequence . the first casing 10 engages with the first thread section 31 of the waterproof screw annulus 30 , and abuts against the inner holding part 20 to generate force f to retain the cable l tightly at one retaining portion . the second thread section 32 of the waterproof annulus 30 engages with the positioning nut 40 and the connecting annulus 50 . at the same time , the metal hose ( wave hose ) s is inserted into the through hole 61 of the second casing 60 , the resilient washer 80 , and the inner buckled nut 70 . the metal hose s is hold by the inner buckled nut 70 . then the second casing 60 is engaged with the outer thread section 52 of the connecting annulus 50 . the slanted portion 802 of the resilient washer 80 is urged by the slanted portion 62 of the second casing 60 to retain the metal hose tightly . the slanted portion 901 of the constricting gasket 90 is urged by a slanted portion 55 of the connecting annulus 50 to deform inward , generating force f to retain the cable at another retaining portion . furthermore , referring also to fig4 , the inner holding part 20 includes a collar 22 and a clamp 21 . the collar 22 is a hollow column , and is made from resilient material . the collar 22 includes a neck portion 221 , a tapered portion 222 , and a broken seam 223 . the neck portion 221 is defined in one end of the collar 22 , and has annular dent . the tapered portion 222 is formed at the other end of the collar 22 , and to be shaped as a hollow cone . the collar 22 can be enlarged by a cable c having a large head ( see fig5 a to 5c ), and facilitates the cable c to get through . the clamp 21 has a plurality of pawls 211 to clamp to the neck portion 221 of the collar 22 . the cable can not store the stress drew by outer force as a result of the resilient column collar 211 . further , the tapered portion 222 of the collar 22 abuts on the slanted portion 34 of the waterproof screw annulus 30 ( referring also to fig2 b ). the collar 22 is urged by the first casing 10 to hold the cable tightly and form another waterproof layer . the preferred embodiment of the invention gives better efficacy on retaining the cable and waterproof than the prior art . referring also to fig6 , the at least one positioning tab 711 is formed at an inner wall of the slot 71 . each positioning tab 71 extends into an inner groove of the outer wave hose for blocking the wave hose from moving out . the resilient washer 80 has wave - shaped structure 801 in the inner surface for fitting the wave hose . the wave - shaped structure 801 extends into the inner buckled nut 70 for further sealing . the wave - shaped structure 801 cooperates the at least one positioning tab 711 to tightly retain the wave hose s from shifting outside , and provide waterproof . referring also to fig7 a , the preferred embodiment of the invention can also protects connectors of a cable l 1 and cable l 2 . a waterproof screw annulus 50 ′ has extended body for receiving the connectors of the cable l 1 and cable l 2 to provide waterproof and shift prevention . referring also to fig7 a , 7 b , 8 a , 8 b , and fig4 , the fastening device also can be inserted into cable connectors c 1 and c 2 having larger heads ( fig7 a and fig7 b ). the connecting annulus 50 ′ has extended body for receiving the cable connectors c 1 and c 2 . furthermore , when the inner holding part 20 is urged by the first casing 10 and the constricting gasket 90 is urged by the second casing , the cables are retained by the forces f . so that the cables has waterproof and shift prevention at two retaining portions thereof referring also to fig9 , showing a second embodiment of the invention , the wave hose s has equal intervals . the inner buckled nut 70 and the resilient washer 80 in the preferred embodiment of this invention are replaced by an inner buckled nut 70 ′. the inner buckled nut 70 ′ is pipe - shaped . an annular stopper 701 ′ extends from one end of the inner buckled nut 70 ′ is used for abutting against a front end of the wave hose s . at least one tab 702 ′ is formed inside the inner buckled nut 70 ′ for buckling and retaining the wave hose s . referring also to fig1 , showing a third embodiment of this invention , the inner buckled nut 70 and the resilient washer 80 in the preferred embodiment of the invention , or the inner buckled nut 70 ′ at the second embodiment of the invention , are replaced by an inner buckled nut 70 ″. the inner buckled nut 70 ″ is pipe - shaped . an annular stopper 701 ″ extends from one end of the inner buckled nut 70 ″ is used for abutting against a front end of the wave hose s . an “ n ”- shaped retaining member 702 ″ is formed on the other end of the buckled nut 70 ″. an annular tab 703 ″ is formed on the retaining member 702 ″ for buckling the wave hose s at the groove thereof . the retaining member 702 ″ can resiliently deform inward slightly . the annular tab 703 ″ has a slanted surface 7031 ″ at an outer side thereof , and a vertical surface 7032 ″ at an inner side thereof . when the wave hose s is rotated in , the wave hose s rides over the slanted surface 7031 ″, and the annular tab 703 ″ resiliently deforms back and abuts against the wave hose s . contrarily , when the wave hose s is drew backwards , the vertical surface 7032 ″ blocks on the groove of the wave hose s for buckling and retaining the cable connector . the above description is given by way of example , and not limitation . given the above disclosure , one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein , including configurations ways of the recessed portions and materials and / or designs of the attaching structures . further , the various features of the embodiments disclosed herein can be used alone , or in varying combinations with each other and are not intended to be limited to the specific combination described herein . thus , the scope of the claims is not to be limited by the illustrated embodiments .