Next, I marked where I wanted to drill the holes for the elastic. Mine are about 4 inches apart. I had to be sure I drilled the holes far enough in from the edge that they missed all the extra plastic ridges on the sides. They're about 1 cm in from the edge on this unit.
Thread one end of the 1/4 elastic through a yarn needle. and start threading it through the holes. I began the threading through the bottom shelf so the knot would be hidden underneath the unit. The ending knot will be on the bottom if you've drilled an even number of holes. Weave it up and down through the holes until you get to the end of one side. Knot several times so it doesn't slip back through the hole (or tie the end to a washer). Then start pulling the elastic tight (I found the tighter the better) working back to the hole you started at. Cut off the extra elastic and knot that end. Do the same on all the other sides. On this unit there are 6 elastic "bars" on the long sides and 2 on the short sides. The whole unit used an 8 yard hank of elastic. For now, that size elastic is working fine. However, if it seems to loosen too much and I'm unable to tighten it with a new knot, I may drill bigger holes and use 1/2" elastic to see if that works any better.
The finished project filled with all of our puppets, a few stray animals and a couple of dolls. We even have room for growth. Not that I'm giving permission to any aunts or uncles to send more stuffed animals...
Coming soon - an easy to sew puppet theater.