"They're the modern equivalent of duct tape and baling wire", says Spouse. These plastic spring clamps, bought at Harbor Freight (I swear, I'm not a paid shill!) are relied upon for many, many things here at the Farm Natters abode. They hold up shade cloths, hold down tarps and blankets, hold closed feed bags, and hold together my sanity. They connect temporary fencing to temporary fence posts (no more need for zip ties or wire), and we even use them indoors for closing chip bags. For temporary attachments and many re-uses, these little babies are darn near worth their weight in gold.
[pic: the clamps, used and abused. Link above goes to their listing at Harbor Freight, if you're interested.]