what do you guys use as build boards?

I use a smooth ceiling tile from the hardware store. My bench is made out of 3/4 inch MDF and is dead flat, so I just lay the tile on top of my bench

I went to my LHS and looked for a damaged door, I found one that had a small hole on one side and I got it for $12.00 Its a 36 inch door. I put it on my table and then I use 4 ceiling tiles I glue these together with the finished side on the inside. This way I can use it until it gets damaged or bad and then flip it over and use the other side. I use two tiles on top of each other so if I need to puch my TEE pins all the way in they will not bottom out. Speaking of TEE pins...... They are expensive.... So I looked them up on EBAY and I found 1000 of them 2" long for I think 6 bucks shipping included. I looked them up under crafts and TEE pins.

Got an old oak library table - dead flat. Topped with ceiling tile turned back side up. Covered with 3/32" cork. Secondary build table is a hollow core door, covered the same way.

Dr.1