Your plans for a folding workbench
It should be noted that:
1. The top and apron should be made from a decent hardwood. Fix the vice through the apron or use a detachable Z-VISE type vice.
2. If you can work out the length accurately so that the frame width for the legs is half the length of the top, the whole thing will look neat folded when not in use.
3. Take time and care to mount the back block and the back (hinge carrying) plates to the wall. Ensure that these are firmly fixed with long bolts or hefty rawlplugs to the wall. The top back block can be drilled or slotted to hold tools, even when the bench is not in use.
4. Make up the end frames and hinge them to the back plates.
5. Hinge the top to the back block so that it folds up and is locked against the wall when not in use.
6. Brace the bench if necessary with a loose bar and a bolt or peg through the apron when in use.
7. If it does not have to fold, then make up the frames and top, back blocks etc, and bolt it all together and to the wall.