William Duffield
Yes, the WorkMate 400 jaws were a previous project, necessitated by my having left the workmutt out in the rain.

The new top is 8/4 hard maple. Note that I made the front jaw about a half inch too deep, and then had to cut some clearance arches for the cranks to get it to open full depth.

I later replaced the masonite bottom shelf with some T&G bamboo flooring. This supports more weight, in the form of sandbags, to help keep the workmutt from walking around while doing heavy work on the metabench. The workmutt is still no replacement for a sturdy workbench underneath, but it is handy for demonstrations away from the shop.