I was having problems with the corners of ABS prints adhering until I tried blocking the cold drafts in my print room from the bed of the printer. So I made three of these brackets, popped them into the vertical rails of my Rostock Mac V2 printer, then cut three pieces of poster board to go between them. No more problems with corners adhering to the bed! In addition, I've noticed that the bed heats a little faster and the temp seems to stay a little more stable.

The poster board pieces I cut were 14-3/4" x 5". Make them too tall and they'll interfere with the arms of the printer.

I made these from ABS. PLA was too brittle to spring the arms open around the vertical rails. The whole system is easy to install or remove in about a minute, and the poster board slips right out for removing your parts or cleaning the bed.