Cutting pieces of wood the same size.

I am not daft enough to think I have invented this method but as I have never been taught anything wood-worky I have no idea what the idea is called?

I started by cutting my pieces of balsa for the books by measuring and marking up each one then I came up with this notion.

Work out where your piece of wood comes to when it is in the block and then clamp another piece of wood to butt up to it.

From then on all you have to do is slide the wood, you want to cut, up to the stopping place made by the clamped piece and you will always have the same desired length.