What do you use to make horse jumps?

PVC is actually pretty good. You have to knock it really hard to shatter it.

I make jumps out of all sorts of random stuff. Drag in some logs from the woods and throw some cheap dollar store flowers around them. Barrels are pretty useful too. Make funky jumps with old tires, old cookie sheets filled with water (look just as deep as any other water to the horse) etc.

you can use 44 gallon drums and barrels lying sideways, tires cut in half, hay bales, tree logs :)