Base Square

Recently I have been getting generic lego type bricks at my local Dollar Tree.

I got this bit of plastic from Amazon, it's one square foot and pretty thick.

It's perfectly square.

It is a half and inch thick.  Very ridged and sturdy and smooth.

It perfectly holds a base square for the generic interlocking pin bricks.  I intend to build a couple very tall buildings and use this heavy plastic as the base for the base.