As most hand-tool woodworking trends get their start these days, I think leg vises gained popularity when Chris Schwarz installed one on his bench which was featured on the cover of his 2007 book, Workbenches: from Design & Theory to Construction & Use.
It seems like every woodworker out there is building a bench and many are incorporating a leg vise.
BenchCrafted is now selling hardware for their Glide Leg Vise.
BenchCrafted has also prototyped a more convenient mechanism, St. Peter’s Cross, which does not require the user to adjust the pin at the bottom of the vise when clamping different thicknesses of material. (Thanks to Charles Mak for the link.)
Jim Ritter of Ancora Yacht Service is now manufacturing a vise mechanism that serves the same purpose as St. Peter’s Cross – the Chain Leg Vise.
That’s all good and well, but I still have one question about leg vises: What’s the big deal?

