At MasterClamp we always felt that something have to stand between the hard wood and a metal clamp, to negotiate, protect, support, and adjust. Welcome the Grubber-Bar, after making couple variants, (beta version), we found this to be the winner, since it is optional, and easy to place fast, and improves the joint quality by 100%.
The reason why it improve goes beyond what we can put in words, it's involved with science, NanoTech, special material such as rubber/neoprene, silicon robber, and alike, all been tested, and selected to be employed for the benefit of maxed contact surface at the joint, protection of the molding etc. Aside of that it allows access from the rear corner joint thus to have hans-on to see, adjust and align, which we know all picture framers like to be able to, (if offered). So there you have it, all you wanted to know about, Grubber Technology, pioneered by MasterClamp for The 2024 line of products.