I had never heard of elastics before reading this thread. Here's another web page about elastics that I found interesting and helpful in explaining how the game was and {probably still is?} played:

http://everything2.com/index.pl?node_id=1841337

Here's a longish excerpt from that webpage which was written by Tem42 on Oct. 21, 2006. Tem42 described how she {he?} played this game in Cape Verde, Africa:

The Basic Idea: You will need three players and a loop of string, rubber bands, or elastic rope. Two players stand inside either end of the loop with their ankles spread slightly apart, the loop pulled tight so as to raise it 3-4 inches off the ground. The third person hops over this rope in a predetermined pattern. If they hop the pattern correctly, the loop is raised up to knee level, and they try the pattern again. Next is hip level (AKA hipsies or underbums); obviously you are not hopping at this point, but leaping. (I have never played with anyone whose hip level was higher than mid-thigh on me, but even so I was exhausted after one round).

Details: The rules, patterns, and penalties vary from player to player, game to game, and often minute to minute. Here are some of the more common variables.

The most common foot placements from which to make patterns are: feet-out-same-side, feet-out-on-opposite-sides, both-feet-in, one-foot-in-one-out (and vise versa), both-feet-out-opposite-sides-but-with-legs-crossed. To these might be added standing on the loop (this doesn't work very well above ankle level), catching part of the loop with your toe, and one-foot hops and jumps.

The loop of string may be crossed in the center (making a figure eight), allowing for more complex patterns. It may be held higher at one end than the other. Turns and spins may also be added. Footwork can get pretty fancy, especially among older kids.

The pattern is usually accompanied by chants, rhymes, and/or clapping. The chants often describe part of the pattern to be hopped...Oddly, there doesn't seem to be much overlap between Chinese jump rope rhymes and everyday jump rope rhymes.

Whether or not you are 'out' depends (usually) on the judgement of the two people playing 'post'. You may be called out for touching the rope, or you may be able to do anything short of falling flat on your face without being called out. Usually it falls somewhere in between, with touches allowed, but trips, catches and stumbles ending your turn. Sometimes it will not be kicking the rope, but breaking rhythm that will be the cause of outs. Often you start your second turn at whatever point you messed up in your first turn"...