with reference to fig3 - 7 there is shown a base clamp 30 for a tubular member 32 which forms a mounting base for another clamp or an extension leg . the base clamp comprises a saddle structure 34 and at least one u - bolt 36 . the saddle structure has a first end , a second end , an upper surface and a lower surface . the lower surface defines a trough 38 extending from the first end to the second end for mounting the saddle structure to tubular member 32 . the saddle structure further defines at least one pair of parallel apertures 40 , 41 positioned one on each side of the trough for receiving a first u - bolt for fastening the saddle structure to the tubular member . a u - bolt having a first end and a second end is received by the apertures and extends over the trough see fig3 and 4 . the upper surface of the saddle structure defines a track 42 configured to receive a shoe the track forms a panel - shaped chamber 44 which is transversely positioned with respect to a radius drawn from a central section of the trough . the track has a track bottom surface 46 facing away from the trough and a roof structure 48 over the track bottom surface which defines a track top surface 50 which faces the track bottom surface and is spaced from the track bottom surface to accommodate the shoe . the roof structure having a slot 52 sized to accept a leg extending from the shoe . the panel shaped chamber and the slot together form an opening transverse to the longitudinal axis of the leg for transverse receipt of a shoe with attached leg . in use , a safety pin 54 ( see also fig9 ) is positioned across the opening to prevent a shoe with attached leg from becoming accidently dislodged . preferably , the saddle structure defines a first pair and a second pair of parallel apertures . the first pair is positioned one on each side of the trough adjacent the first end of the saddle shaped structure for receiving the first u - bolt for fastening the saddle structure to the tubular member . the second pair is positioned one on each side of the trough adjacent the second end of the saddle shaped structure for receiving a second u - bolt 37 for fastening the saddle structure to the tubular member . see fig5 . the first u - bolt has a first end and a second end which are received by the first pair of apertures . the second u - bolt likewise has a first end , a second end , is received by the second pair of apertures , and extends over the trough . the saddle structure also preferably further defines a port 56 to permit unobstructed passage of a fastener bolt 58 ( see fig4 ) therethrough positioned between an aperture of the first pair and an aperture of the second pair . the track 42 can connect the base clamp 30 via a support leg to a line clamp according to another embodiment of the invention for a tubular hose or cable . the line clamps illustrated in the figures are variations of each other and will be described with different reference numerals . the line clamp shown in fig1 will be described with 100 series numerals , while the line clamp shown in fig2 will be described with 200 series numerals . with reference to fig1 and 2 , the line clamp 102 , 202 comprises an upper clamp half 104 , 204 , a lower clamp half 106 , 206 , a hinge pin 108 , 208 connecting the halves , a fastener 110 , 210 latching the halves , and a support leg 112 , 212 having a shoe 114 , 214 ( see fig1 - 13 ). the upper clamp half has a downwardly facing parting line face . the lower clamp half has an upwardly facing parting line face and is positioned in a face to face relationship with the upper clamp half so that the parting line faces are side by side . the hinge pin pivotally connects the clamp halves along a hinge edge . the fastener connects the clamp halves along a latch edge . the support leg extends from the lower clamp half and has an upper end attached to the lower clamp half and a lower end . the shoe is positioned on the lower end of the support leg . the clamp halves , when positioned in a face to face relationship , form a clamp assembly which defines at least one passage 116 , 216 therethrough for clamping a cylindrical object , such as line 60 shown in fig5 . the passage has a longitudinal axis and the clamp assembly parts along a parting plane which encompasses the longitudinal axis . the support leg has a longitudinal axis which extends normally to the parting plane . see fig1 and 2 . in a preferred embodiment , the clamp assembly defines a pair of passages extending therethrough in side - by - side relationship . even more preferred , an elastomeric liner 120 , 220 lines each of the passages which extend though the clamp assembly 102 , 202 . preferably , each elastomeric liner comprises a pair of liner halves 60 ( see fig1 - 20 ) positioned in face to face relationship . each liner half defining at least one trough 62 . one liner half is positioned in each clamp half . each passage through the clamp assembly is defined by a pair of facing troughs from facing liner halves . in a preferred embodiment , each trough is semicylindrically shaped . a layer 64 of an anti - skid material positioned in each of the semi - cylindrical troughs . most preferably , the layer of anti - skid material comprises a screen 66 which is coated with abrasive particles . in order that the liner resist dislodging during handling and use , it is preferably provided with a flange 68 on each end . each of the flanges preferably has a lip 70 which extends toward the opposite flange and retains the liner half in position on the clamp half . where a low profile is not needed , the preferred assembly employs a fastener as shown in fig1 . the fastener comprises a bolt 158 which extends upwardly and has a wing - nut 160 attached . the head of the bolt is attached to a portion of the lower clamp half and the shaft of the bolt extends through a portion of the upper clamp half and protrudes upwardly . where a low ( or lower ) profile is desired , an assembly employing a profile as shown in fig2 can be used . the fastener comprises a bolt 258 having a head which contacts a portion of the upper clamp half and a shaft attached to the head which extends through a portion of the lower clamp half and protrudes downwardly . a port is preferably provided in the base as previously discussed to permit passage of the bolt . as shown in fig1 and 10 , a flange 170 can be positioned on the support leg between the upper end and the lower end of the support leg which is of the same shape as the shoe . this permits the length of the leg to be easily modified , in the field if necessary . if a longer leg is necessary , the track on the base clamp can connect the base element to an extension leg 172 . see fig8 . the extension leg has a first end and a second end and a longitudinal axis extending between the first end and the second end . a shoe 174 is positioned on the first end of the extension leg . a track 176 is positioned on the second end of the extension leg which is configured to receive the shoe . the shoe is panel - shaped and extends transversely to the longitudinal axis of the leg . the track forms a panel - shaped chamber , preferably identical in configuration to the chamber in the saddle structure , which is transversely positioned with respect to the longitudinal axis of the leg . the shoe has an upper shoe surface facing the leg and a lower shoe surface which faces away from the leg . the track has a track bottom surface facing away from the leg and is configured to fully support the lower shoe surface of the shoe . the track has a roof structure over the track bottom surface which defines a track top surface which faces the track bottom surface and is spaced from the track bottom surface so to contact the upper shoe surface and closely position the lower shoe surface of the shoe against the track bottom surface . the roof structure has a slot sized to accept the leg . the panel shaped chamber and the slot together form an opening transverse to the longitudinal axis of the leg for receipt of a shoe and leg . a safety pin , which can be the same as the pin 54 , is preferably positioned across the opening to prevent the shoe and leg from becoming accidently dislodged . certain aspects of the liner have been previously discussed . the lips on the liner end flanges combined with its elastomeric construction permit the liner to be snapped onto a clamp half to facilitate handling and reduce the likelihood of accidental dislodging . the anti - skid material can be positioned with a layer of adhesive material positioned between the elastomeric liner half and the layer of anti - skid material , preferably a water - proof adhesive . suitable anti - skid material is commercially available as sanding screen and can be purchased in rolls . a coarse plastic pipe sanding screen has been used with good results . such screen is waterproof washable , has an open mesh backing , and is coated with abrasive on both sides . the coated abrasive comprises sharp silicon carbide particles . the elastomer generally has a durometer of between about 70 and 130 , preferably a durometer of between about 85 and about 105 . nitrile rubber having a durometer of about 95 has been used with good results . in the illustrated embodiment , the outside wall of the liner half defines half of a side - by - side tubular surface . the inside wall of the liner half defines flats for abutting corresponding flats on an inside wall of an opposed liner half the illustrated and described clamps have consistently provided a clamping force of over 2500 pounds . while certain preferred embodiments of the invention have been described herein , the invention is not to be construed as being so limited , except to the extent that such limitations are found in the claims .