Composite objects, like frames, should have holes in all the corners at the leading ends. All the corners of the joints should also have holes, or the joints should be entirely open.
This drawing shows the various ways of putting together, for example, a frame. Holes have been drilled in all the corners at the leading ends. The top of the structure includes two joints that are less suitable for galvanisation, if at all, because the hole is in the middle or because there is no opening at all. The bottom includes two joints that are both highly suitable for galvanisation. The first joint has holes in every corner; the second joint is entirely open without the slanted section being pushed through the section it links up to, ensuring there will be no air pockets.