what jack said, i do the same, and i use shallow or medium boxes to house insulation that goes over the inner cover, or make vent boxes out of them. i will also staple window screening on the bottom of a medium super and use it to collect scrapings, and when i clean out a dead hive, the debris goes in it. i used to use these too to house hay for insulation in the winter. also, when i am cleaning frames off after extraction or a dead out, it's nice to have an extra empty box to set the cleaned frames in so i can scrape the useable box clean. when they finally fall apart, they go in the fire pit.
how do you use yours ef?