[QUOTE=Janet;7854632]
I beg to differ.
At Upperville the warm up jumps WERE flagged.[/QUOTE]
Also at Indoors, even for the hunters. That one’s easy enough, though. If you see flags on the jumps, don’t go the wrong way.
Really, as long as you follow the rules for tack and attire, you’ll be fine. And if you don’t have anyone to set jumps for you, a polite, “Hey, do you mind if I hop over your jump a few times?” followed by, “Thanks very much!” should work quite well in most situations. 
USEF jumper rules:
https://www.usef.org/documents/ruleBook/2014/18-JP.pdf
