it as shown by the dotted line 42a and get increasingly tight as the load increases or the jaw is displaced very slightly as shown by the dotted line 40a in fig1 consequently the roller adapter and the carriage mounted to it cannot slide along the rail as mentioned above it is highly preferred that the length of the series of serrations from the leading tooth to the trailing tooth in the direction of the rail this being a direction transverse to the roller and bolt axes and in a plane parallel to the plane of the bottoms of the support rollers where they engage and are supported on the top flange of the rail be relatively short and preferably no greater than 75 of the distance from the nearest of the teeth to the bolt both clamp jaws on the bolt are the same the typical shape of the serrations is saw tooth with an included angle of from 85 u00b0 to 95 u00b0 and a tooth depth from the crest to the root of 0 04 to 0 06 inches the material is preferably sae 6150 steel with a black oxide finish and hardened to 40 45 on the rockwell c scale the bolt threads are typically 5 8 18 unf 2b one being left hand thread and the other being right hand thread the overall distance dimension l in fig5 from the outside of the first tooth 42 to the outside of the last tooth 43 is nominally 0 750 inches while the invention has been illustrated and described in detail in.