I use plastic containers with snap close lids. For longer pieces I stand them up in a deep plastic beer stein which has some weight added to the base (resin and lead shot). One contains styrene another contains metal tubing, angles, rods, wire and flat stock.
You can see the beer steins behind the lamp on my bench...their from some steak house in the Dallas area LOL
The flat totes are on the shelf on the upper left of this pic the ones with Blue lids.