These aren't vise clamps your dad made in Dewitt-Nebraska. The adjustment screws are very sloppy and if you are not careful they will lose their adjustment when loosened. I bought four of these to work on the new roof and held the mahogany support blocks under the plywood deck through the rake while they were bolted on. I bought them because my old (bought in the 90's) 6" Vise-Grip C-Clamps didn't fit where the blocks were. Every time I opened and moved these clamps, the pressure changed. The set screws on the old clamps are tight enough to be easily adjusted, but they don't rattle in the threads. They are very cheap but there is no excuse for such a sloppy fit.