I saw a photo on the Internet last year and finally built myself of these
Here's the prototype, just like the photo, but the top support interfered with my magnifier so I hacked it off:
Second version had support in the back instead of overhead.
I wanted to lightly insulate the back of the box so the brood wouldn't get chilled if I took my time grafting. My halogen light is nice and warm without being too hot. I can cover the frame of larva with a damp paper towel, then go have my coffee or lunch if I want to without feeling rushed.
Back side is just a scrap piece of twin wall poly carbonate. I also made a interior frame so the back of the comb wouldn't get squished. A damp paper towel in the back will also keep the larva moist. The poly carbonate pulls right out for cleaning and is easy to wipe off wax or sticky stuff.
Could have used a wing nut..just didn't have one handy.
Love this halogen magnifier. Makes eggs look like hot dogs. (This is just my grid frame..not yet in use What you see is open nectar from last year in the cells) Amazon.com had lots of magnifiers to choose from
Simple box with a cleat on the back works too and is lower to the counter.