Someone on another forum was asking about my bench after seeing part of it in a photo of some WIP, so I prepared an explanation and thought I'd post it here too for anyone who is interested.
To start, I should say I dont like bench dogs. I need to use my bench for all sorts of things including repair of electrical devices, assembly etc, not just woodwork, and a large number of holes where small screws etc fall through into the sawdust is an absolute no-no for me. I use clamps to hold work.
Hence this design. It comprises a very solid base, 10" x 3" joists, carefully leveled by hand planing, to support two torsion boxes each consisting of a top and bottom layer of 3/4" MDF glued and screwed over a 3" framework. Then a top layer of MDF is glued on to cover all the fixings.
These are spaced apart by around 10" and the space filled by 3 boxes sized so that they are exactly level with the bench top. The outer edge is reinforced by an oak rim/frame to resist the knocks and abuse of day to day work ! The back jaw of the vice is integrated into this.
The boxes provide a level(ish) suface for day to day activities and apart from the two finger holes, there are no significant opportunities for components to fall through ! One day I'll add a closure under the finger holes but it has never been a problem.
Take a box (or boxes) out and you can clamp to the middle as well to the outside of the bench.
You can also use a jigsaw on large sheet goods which are well supported over the whole area of the bench.
For assembly jobs, it is also possible to put the box(es) in upsidedown to act a tool stores while still allowing work to occupy the whole bench surface.
I tend to leave the box at the end in this mode for parts relating to current jobs. It gradually fills up with clutter and needs a periodic tidy up !
It is critical that the two torsion boxes, which are super rigid, are exactly co-planar so that clamping glue-ups etc can span the two and remain truly level. This comes down to good preparation of the framework underneath. Mine is within about 1/2mm over the whole surface.
The idea is not original, I saw something similar in an edition of FWW years ago and adapted it. This is in fact the second one I've built and includes a few improvements over the first !