Anybody got any ideas for relatively easy, inexpensive obstacles for some backyard practice?

Hi Charlie, the same question was asked a while back, have a looky HERE - old tyres, logs, rocks and barrels all tend to be free or cheap if you look around?

GJ

I get two, three or four logs (12 to 18 inch thick) and I tie them together with galvanised guy-wire ( as used on rotary clothes line ) and tighten them with a small turnbuckle - you can vary the height and depth of the obstacle easily or even stick a few bricks underneath the middle logs - I find it quite stable for my use. The wire doesn't seem to get in the way and is gentle on the tyres.