the t shaped clamp 421 inside the groove 410 allowing the fence face 402 to slide out of position parallel to the fence beam 404 as shown in fig4 b the lock knob 432 is connected via a shaft 444 to one or more threaded regions 442 in the exemplary embodiment of fig4 b the adjacent threaded regions 442 include oppositely arranged threads although the threaded regions may include threads in the same direction a follower nut 440 a 440 b is fastened on each threaded region 442 each follower nuts 440 a 440 b is attached on two ends to two links 446 of the t shaped clamps 421 the links 446 are attached to a lock face 448 of the t shaped clamp 421 at fixed positions turning the lock knob 432 clockwise causes the threaded regions 442 to turn via the shaft 444 as the threaded regions 442 turn the upper follower nuts 440 a 440 b traverse in the longitudinal direction away from their original unlocked position in this example since the threaded regions 442 include oppositely arranged threads the follower nut 440 a traverses away from the lock knob 432 and the lower follower nut 440 b traversed towards the lock knob 432 as the follower nuts 440 a 440 b move.