The ad for the "Transformer Ladders"
When it gets to the part where the guy says "And out comes the insert, and now you have two trestles"
As the insert comes out (it has the top rounded bracket attached) it leaves the outer part,, which does not have a top rounded bracket.
Yet,,,,,,, the next frame shows the two trestles,,,, and both of them now magically have the top rounded bracket attached to them.