Time: Barely any
Skill: Not much
Step 1: Materials
- Corrugated cardboard; the thicker the better
Optional, But Will Make Things Easier
- Tape measure
- Ruler or other long, straight object
Step 2: Building It
I trust everybody has something knife-y already.
Measure the the locker/cabinet/wherever the shelf is going. Either use the tape measure or just hold the cardboard up to the thing and mark off the size needed. A few millimetres off won't make too much difference, but it's better to have a bit too much than not enough.
Once the top part is cut, measure the desired clearance and cut the side supports.
Run the corrugation "grain" crosswise for the shelf platter, and vertically on the supports, for extra strength. Thinner stuff especially can begin to sag under heavy loads.
Step 3: Organize All That Crap
Want it all fancy? It's cardboard. Once it's sized to fit the locker, grab some craft glue and old magazines and découpage it. Paint it. Papier-mâché it.
The plastic boxes stuck to the door are my Sugru'd Dremel burr cases.