Someone posted this link in a recent thread:

I was reading the section about separating the worms when it was time to harvest. I wasn't quit sure what they were saying in the text below. To me, it seemed like they were saying to put a screen on top, add some fresh bedding, let the worms migrate up, remove the screen along with the top layer, and then harvest what was left down below. However, upon a second read, it seems like they are saying something different, and I don't think it makes sense. Here it is:

Even less hassle -- vertical separation

Get a piece of nylon or mesh window screening a bit bigger than the surface of the box and lay it flat on the surface of the vermicompost. It should be big enough to flatten against the sides and leave some overlap at the top. Fill the box up with fresh bedding on top of the screen and continue feeding it with kitchen scraps. The worms will migrate up through the screen into the new bedding as the food runs out below.

When the top part is ready for harvesting, use the overlap to lift the screen from the box, vermicompost, worms and all. Set it aside and empty the box -- it will have a very high concentration of worm castings and few if any worms, hatchlings or capsules.

Dump the wormy material that was on top of the screen into the bottom of the box and put the screen back on top of it, with fresh bedding on top of the screen.

Check the condition of the screen each time you empty the box, and replace it before it gets rotten enough to rip just as you're removing it, spilling everything back into the box.