Here is a Knex target that I have made. As far as I am aware nobody else has used an elastic band in the exact way I have. (Yes people have used elastic bands for targets but not 'exactly' in this way. It is held up and can easily knocked down by a low power knex gun, as well as the high power ones. It is very important that it is on a flat surface otherwise it doesnt work. Also, the length of elastic band is important. I might make an ible of this if I have the time. Here it is!