invisible glitch

when I made the level watch... learn... I worked a lot with custom shapes. One time I wondered when at a certain point you would remove one point of the shape. at first I got at shape where you where able to ride through the custom shape. But later when I saved and loaded it again all the shapes were gone but you could still ride on it. In the level itself on the left you will find what sort of shape you have to make and you see a cross through the point you have to delete. You can make cool levels with this glitch, I gave you some examples. If you already know the glitch please comment because I actually dont think im the first one to find out. I did search on youtube and in the gallery if I could find something like this but I could not find anything. hope you like it.