Foam blocks that sit perfectly on the inside of the A4 and A3 frames for use during screen exposure.

Foam block measurements: 
A4 Foam block: 23cm x 33cm
A3 Foam block: 33cm x 44cm

Both are 6cm thick.

Use the foam block to keep the screen flat to the transparency, use a piece of glass above the transparency to keep the transparency flat to the screen.