It seems perplexing that since the control joint was invented by Raymond Clark in 1955, there have never been large-scale tests of the function and movement when subjected to shrinkage or thermal variations. The design was not complex. It’s what is known in today’s market as the double V or M expanded flange control joint (Figure 1). This design hasn’t changed much since conception. One thing that is justified to mention is the original design showed the joint tied to lath that was continuous behind it. The patent was filed in 1962 and it has been used in exterior stucco applications ever since.