basically it makes you automatically jump i just came across it when i was playing in my server and i thought why not :P so yea set it out how it is in the picture and jump for hours! :D This is all legit!

i dont know if this is a bug / glitch etc but i think its kool

Tut:
1. get any desired block stair and a minimum of 2 iron bars
2. make a 5 Long and 3 Wide Ditch
3. the middle block at either end has to be a stair block.
4. now place the iron bar above it, it has to be 2 / 3 wide.

Try it out!