Push/Pull not creating 3D object?

So I have 3 rectangles on the ground, arranged in a U shape, all touching at the ends.
When I use push/pull on one of them, I expect it to turn it into a 3D box. From the top, it looks normal:
But then I look at the bottom:

It has not created a 3D object, it has created more 2D surfaces. Why? Am I doing something wrong? Do I have to change something in the settings?

By the way, it works fine when there is only one rectangle on the ground.

Push/Pull is doing exactly what it should. Because the of the attached rectangle, what you are doing is the equivalent of pushing a hole through a box as in making an opening for a window. There are a couple of options to prevent that happening. Make groups or components of the rectangles so they aren’t stuck together, Make the extrusion before drawing the next rectangle (but if you’ll extrude it, too, you’ll want to make it separate from the first. Or you can hit Option prior to running Push/Pull to make it create an additional face. You’ll probably have to correct face orientation after that.

What is it you’re trying to draw?

Thanks. Hitting option works great. That picture is just from an example sketch I made, but I had the problem while working on some windows for a simple house.

Just because that worked, it doesn’t mean it is necessarily the right way to handle it.

So which would you say is the right way to handle it?

It depends upon what you really need for a final component. For a window frame that you don’t need to disassemble, draw the frame as a rectangle with a rectangular hole in the middle. Then use Push/Pull to make the entire thing 3D to get a sort of donut with corners. If you need the seam lines between the stiles and rails, draw them in after making it 3D. Or, if you need to be able to disassemble the thing as you might for a construction drawing of the window, draw a stile and make it a component, then draw the rails and make them components to prevent the geometry from being glued together.

There are other options for components such as windows but as I said, it depends upon what you need out of it as the end product.