To play simply get a solid stick (a broom handle works well) and hold it in both hands in front of your body. Hands should be shoulder width apart. Now the objective is to jump both feet off the ground at once and through the stick without releasing your grip and land without toppling over. You should now be in a slightly crouched position with the stick behind your knees. Now, simply, jump both feet backwards over the stick to return to your starting position. Repeat until exhausted.
There is a modern day equivalent of Jump Through Stick, namely Underpants Jumping (or the Sport of Philanderers as it is sometimes known). Keep your clothes on and use a spare pair of underpants - old ones where the elastic has gone may be the best, but avoid the use of the thong. The game is simply to hold the pants then jump both feet simultaneously into them and then pull them up to your waist, take them off and jump again. Players play against the clock to see who can do the most underpants jumps within a set time. See the video in the link below for some pantastic players.
strange games no:144 &145
note: the accompanying picture shoes the German Record Holder (Hans Skidmarx) in action