with reference to fig1 , a metering rod assembly is illustrated and identified generally by reference numeral 10 . the metering rod assembly 10 is illustrated as a component of a machine for applying a coating to paper during a paper manufacturing process . it will be appreciated that the metering rod assembly 10 is supported by a support 12 adjacent a roller 14 which advances a web of paper 16 between the metering rod assembly 10 and the roller 14 . although not shown , it is well known that an applicator is generally provided upstream of the metering rod assembly 10 for applying a coating liquid to the web 16 . the coating is applied in excess and the metering rod assembly 10 is utilized to remove excess coating from the web 16 to achieve a desired coating thickness . the metering rod assembly 10 generally includes a base member 30 that is mounted to the support 12 . with additional reference to fig2 and 3 , the base member 30 includes a channel 34 opening to a face or surface 36 thereof . the channel is generally defined by first and second sidewalls 40 a and 40 b that are spaced about a central plane a - a of the channel 34 . in this embodiment , the first and second side walls 40 a and 40 b of the channel 34 extend at a non - zero angle 41 relative to a central plane a - a of the channel 34 such that the mouth of the channel 34 is wider than a base portion of the channel 34 . the channel 34 further includes upper and lower retention slots 42 a and 42 b for receiving corresponding retention elements on a rod bed insert , as will be described below . a rod bed insert 46 is received in the channel 34 and includes a metering rod slot 50 in which a metering rod 54 is supported . the rod bed insert 46 is configured to be closely received within the channel 34 , with first and second sidewalls 56 a and 56 b of the insert 46 have a mating shape and slope to the first and second side walls 40 a and 40 b of the channel 34 . the rod bed insert 46 includes a narrow or necked - down portion 57 connecting the first and second sidewalls 56 a and 56 b and a pair of spaced apart parallel longitudinally extending slots s allowing the insert 46 to flex about the necked - down portion 57 to accommodate insertion and / or removal of the metering rod 54 from the metering rod slot 50 . the rod bed insert 46 includes a pair of tab portions 58 a and 58 b that serve as retaining elements when the rod bed insert 46 is inserted in the channel 34 . as best seen in fig1 and 2 , the retention tabs 58 a and 58 b extend into corresponding retention slots 42 a and 42 b at the base of the channel 34 . once the tabs 58 a and 58 b are secured in the slots 42 a and 42 b , the interference between the tabs 58 a and 58 b and the base member 30 restricts withdrawal of the rod bed insert 46 from the channel 34 . returning to fig1 , a pressure tube 60 is supported adjacent the base member 30 and configured to apply a force along the plane a - a to place the metering rod 54 in compressing engagement with the roller 14 , as is conventional . in the illustrated embodiment , the pressure tube 60 acts along the plane a - a . the pressure tube 60 can also be configured to apply pressure along a plane offset from the plane a - a . unlike prior art metering rod assemblies , a single pressure tube is utilized to not only place the metering rod 54 into compressive engagement with the roller 14 , but also to clamp the metering rod 54 and / or rod bed insert 46 in the base member 30 . to this end , it will be appreciated that when force is applied to a rear surface 64 of the base member 30 , the force is transmitted through the base member 30 and rod bed insert 46 to the metering rod 54 . a reactive force is applied to the metering rod 54 by the roller 14 which tends to force the metering rod 54 deeper into the rod bed insert 46 . the net effect is that surfaces 40 a and 40 b are urged towards each other thereby clamping the rod bed insert 46 and / or metering rod 54 in the channel 34 of the base member 30 . as the force urges the insert 46 deeper into the channel 34 , the interaction of the sloping surfaces 56 a and 56 b with sloping surfaces 40 a and 40 b urges the sides of the insert 46 together gripping the rod more tightly . it will be appreciated that , for a given pressure applied to the base member 30 by the pressure tube 60 , the clamping force can be altered by changing the angle of surfaces 40 a and 40 b relative to the plane a - a . for example , a relatively shallow angle , such as 20 degrees , will produce more clamping force on the rod bed insert 46 than a relatively steeper angle , such as 40 degrees . accordingly , depending on the specific application , the clamping effect can be tuned to achieve desired performance . for example , an application requiring light pressure on the metering rod may benefit from a relative steep angle of side walls 40 a and 40 b ( greater clamping force at lower pressure on the metering rod ), while an application requiring higher pressure on the metering rod may benefit from a more shallow angle ( less clamping force at higher pressure on the metering rod ). turning to fig4 , another exemplary metering rod assembly is illustrated and identified generally by reference numeral 80 . this embodiment is essentially identical to the metering rod assembly 10 of fig1 - 3 , with the exception of a hinge feature of the base member . accordingly , the assembly 80 includes a base member 82 having a mounting portion 84 adapted to be secured to a support ( not shown ), a head portion 86 , and a reduced cross - section hinge portion 88 connecting the head portion 86 and the mounting portion 84 . a rod bed insert 92 is received in a channel 94 of the base member 82 in a similar manner to the rod bed insert 46 of fig1 - 3 . the channel 94 includes first and second side walls 95 a and 95 b spaced about an axis or plane b - b . in this embodiment , the hinge portion 88 facilitates flexing of the head portion 86 relative to the mounting portion 84 when a force is applied to the head portion 86 , such as by a pressure tube ( e . g ., pressure tube 60 of fig1 ). such flexing generally rotates the head portion 86 counterclockwise relative to the mounting portion 84 such that an upper jaw 96 including side wall 95 a is urged towards a lower jaw 98 including side wall 95 b thereby clamping the rod bed insert 92 and / or a metering rod in the channel 94 of the base member 82 . in this embodiment , it may be advantageous to position the pressure tube to apply force to the head portion 86 at a position above plane b - b to increase the levering effect and clamping force generated . as with the embodiment of fig1 - 3 , the angle of side surfaces 95 a and 95 b relative to plane b - b can dictate the level of clamping force generated when the metering rod assembly is in use . unlike the previous embodiment , however , the present embodiment optionally allows for elimination of the angled side walls of the channel 94 since the upper jaw 96 is urged towards lower jaw 98 resulting in a clamping effect independent of the clamping effect generated by angled side walls . the exemplary embodiment has been described with reference to the preferred embodiments . obviously , modifications and alterations will occur to others upon reading and understanding the preceding detailed description . it is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof .