You probably can, but a better idea is to attach the bench vice to a board and clamp the board between the jaws when you need it.
@Tom: Mine is from 1975 and is worn but in good shape. I've been touching up paint chips and making my own replacement parts from general hardware.
The bottom legs fold under to give you a 2nd lower working position, and the whole upper frame folds down for storage. Love my Workmate!
It is not thick enough or sturdy enough for a bench vise. You really need a BIG bench in my opinion.
9.5" between the slats and 16" between the plastic dogs.
Of course, but it won't fold flat with them attached to the legs.
You can also go to Home Depot and buy one piece of 1x6 hardwood board and using one of you old boards as a pattern, make your own. I have just bought a new table and made a spare set of boards.
Yes, if it's smallest dimension is 16".
You need to reassemble it. There are three adjustment slots along the topside for placing the back board to adjust the closing distance.
You can ask, but there are YouTube videos on how to do it. https://www.youtube.com/watch?v=WAoL14J_T_o All models assemble similarly.