Yesterday I used the two long foam Durablock's to block my fiberglass deck lid. I had two heavy coats of polyester primer on it and wanted to block it getting ready to apply some 2K primer. I cannot imagine an easier blocking system than the Durablock. I was also using the 3M guide coat system and it worked great also. The hard foam blocks conformed perfectly to the curvature of the deck lid allowing full sweeps from one corner to the other and from top to bottom., great product IMO.