Zippers are usually attached to something.

Is this design practical? What would it be used for? With this zipping mechanism, can anything be attached?

Edit: Apparently I stopped watching the video too early. They demonstrate some uses where at max only one of the three sides can be attached to something, and it is used to create a rigid structure rather than joining multiple surfaces. The most interesting use demonstrated (IMO), is a tent with no tent poles, but it doesn't look like it would hold up to any significant weather, and would probably take up just as much space and weight as tent poles.

Poles. The video shows a tent they set up just by zipping up the y zipper.