The sliding jaw on one of my small bar clamps lost the ability to engage the bar and became unusable. To salvage the clamp, I drilled a hole all the way through the jaw and several evenly spaced holes along the bar. The clamp can now be used through its full range by inserting a nail through the sliding jaw and into any of the holes in the bar that offers the capacity I need.
-Jim Moorehead
Barrigada, Guam