I've been assembling some deep frames I got from dadant, grooved top and bottom with plasti-cell foundation. Two corners of each sheet of foundation has a diagonal perforation. My guess has always been that you could break those corners off and the bees could use the opening as a "pass through" to get to the other side. Looking at it today, that thought seems silly as they could just walk around to the other side just as easily. The question is, what are the perforations for? Do they serve a purpose? Do they occur during the manufacturing process, the waxing process? Inquisitive minds want to know!