I've begun to show my work at some local art fairs. I currently transport the pictures in a minivan in cardboard boxes (30 inches wide, 25 inches high, 5 inches deep). I load four framed pictures per box, separated by poster board. I've seen other photographers using plastic or metal boxes that are sturdier and more protective than what I'm doing, but have not had a chance to talk to them while at the fair. Another major concern is moving the boxes in the rain when I can't get the van near my location. My pictures are various sizes, from 18x18 inches to 18x29 inches, framed.

The question - what other methods are used to transport pictures to and from art fairs?

Thanks