I have seen some pics on here of someone using the metal spring clamps (kinda like large clothes pins) to hold equipment in an enclosed trailer. They just screwed one side to the wall with the gripping part up and set items in the clamps.
They do cost some money, but greentouch sells nice heavy duty racks. They also have a rubber coating to protect your equipment.I look at it like this, all the money I spend on backpack blowers and trimmers/edgers I want them to stay where I put them in travel.
I had my weedeater string holder from a garage hook that I bought at Home Depot for about $5 looks just like the ones for $25. and I had it in my enclosed and now on my open trailer.there is pictures on the site here.