I guess that "plus-like protrusion" is designed to fit "tubes" on the high bricks, primary use being removing low bricks from high bricks. I guess one could use

I guess that "plus-like protrusion" is designed to fit "tubes" on the high bricks, primary use being removing low bricks from high bricks. I guess one could use two separators side-by-side to firmly hold 4x2 brick, IIRC 2x2 had one "tube" and 4x2 had two "tubes".