Problem with plans

Probably that I just don’t know the trick but it drives me nuts. I’m a welder and I roll material to make arches. Let’s take a piece of tubing 1”x2”, to create it in shapr I trace my arc and create a plane at the end perpendicular to my line. Then the idea is to draw a rectangle 1”x2” from its center at the point “end of the curve”. It is just impossible to do it and I don’t understand why.
Here is a screenshot. Last step is of course to sweep to create the body. Thanks.

Here’s how I did it. I started the 1"x2" rectangle 4" above Y plane. I also started the arc 4" above. The rest is self explanatory. BTW, I didn’t need to create a plane.


Thank you again for the help. Don’t you think it would me useful to be able to creat a point in one plan that would be reachable in others.