Trials obstacles

hey
ive been riding my uni for a few months now and seem to have got that hang of it quite fast. Im interested in trials and have set up a few lines in my back yard. So far ive been using things held up by bricks and logs, ive built an alright sandwhichboard but does anyone know of any good obstacles i can build with basic materials?

Here are some links that might help:

thanks

thanks alot;)

This may help - http://munimanpete.unicyclist.com/building.pdf

Good luck,
Andrew