I assume you mean an agility or rabbit hopping jump? If so, they are fairly easy to make.
The ones I make are done with 1X2" posts. The bases are 5x7" things from Michaels, but you can use other stuff that is around 1/2" tall. Taller jumps do need bigger bases or they tend to tip. For a 2ft jump, I use bases that are around 6X12". The smaller bases are for 1ft tall jumps. You also need poles that are 2 or 3 feet long, I use 1/2 inch ones. Jumps cups are file canisters. You just then need screws to go up through the base into the post (2 per jump) and enough for each jump cup (around 18-20 for a 2ft jump). Paint is also good and any decorations you want.
To build it, mark the middle of the base and how big the posts are, then mark where you want your screws. Drill holes for the screws in the base and the post, make sure they line up. Screw them together. Measure up the posts how far you want to bars to be. I do 2.5" between the bars, but would not do more than 3" though for untrained rabbits. Mark where you want each jump cup and drill as small hole. Make sure the holes line up on each post. Cut the film canisters. Just cut it length wise leaving the bottom intact. You want to take around 1/2 of it off. Drill a whole in the centre then screw them on. If you want to paint the stand, do it before you put the jump cups on. Paint the bars (I put a bit of tape on the jump cup and put the bars on to dry. Any decorations can then be glued on.
If you are just going to do the jumping at home on carpet, 2ft long poles should be good. It will be wide enough for the rabbit to get through but not too wide that the jump gets in the way. This is fine if you are going to use the jump on carpet or grass or another surface that is safe to run on. The club I am in uses mats that are 2ft wide. This poses a problem in that 2ft wide poles are not long enough. There are 2 solutions, 1 is to use longer poles and cut them so they it without allowing too much extra space (28" works), the other is to put the posts on the edge of the base so the jump cups go over the mats. You can also use thinner bases that you slide under the mat.
There are a few important things to remember when building jumps. They need to be safe for the rabbits. The bars should fall off easily. The film canisters can break (and are easy to replace), so that also helps prevent injury. Sometimes the jump will fall over if the rabbit kicks out or falls. Only jumps under 4" can be solid, anything taller needs to be able to fall for safety.
You also want jumps that are easy to run beside. Our jumps used to be 3ft wide and a couple had posts that were over foot wide in addition to that. This made it difficult to run around the jumps. Now all the jumps are right along the course and are short so much easier to get around.
http://canadianrabbithoppingclub.com/HTML/equipment.html 
