The best way to brace greenhouse arches is to engage a hole drilled into the end of a 2x4 with the bolt in the arch peak. However, the supplied bolts (on the left and the right in this picture) are too short to serve this purpose: As the structure warms on a sunny day, it expands, and the brace drops out. The solution is to install longer peak bolts at the time of construction. When the hole in the brace is engaged with the longer bolt, it does not drop free when the arch expands.