The ball cannot pass over the top of the backboard (rectangular) in either direction. But say a shot is taken and the ball bounces off the rim, bounces on the top of the backboard and comes back down toward the side of the rim. When is the ball out of bounds in regards to the top of the backboard?

When it passes over. Until then, play on.

When it goes over the backboard.
The top of the backboard is not OOB. However sometimes the ball contacts part of the basket/backboard support structure near the top and is OOB due to that contact. Same contact can happen with a shot clock mounted near the top of the backboard.

Unless it is a Fan-Shaped backboard. The top of that board is OOB.

In your example the ball is passing east-west along the backboard's width & is legal.

The ball is OOB when it passes directly over the top of the backboard going north-south or from the front face to the back face.

If that makes sense to you.

You should look into that a little more.

So you are the official that has been telling coaches these "facts" all along? :D

You are correct that my post does not apply to a fan-shaped backboard. I am replying to this post that specifically mentions a rectangular backboard. In addition I am replying to the poster who pointed out he is aware the ball cannot go over the top of the backboard.

As others have posted, you are incorrect about a fan shaped backboard. The top of the that backboard is not OOB.

Sam, That last response really cleared it up????
I do not have my book here but this is the best way to describe it I can think of
Rectangular backboard - if the ball rolls along the top of the back board and does not come in contact with any any support or timing device mounted on the back board and falls either down on the rim side of the board and or either end to the right or left of the basket it is NOT OOB, and remains a live ball.
If the ball comes incontact with a recessed timeing device - or support structure on the top of the back board or goes over the back board (rectangular) it is OOB and becomes a dead ball.

Assuming that it came from the front side in the first place, right? What if it came from the back side? ;)

There is always one in the crowd.
Thanks for the clarification.

That is an incorrect statement, the ball can role along the top of a rectangular backboard and still be in bounds. The top is not OOB.

Reading comprehension = 0/1
Spelling = -1

The difference between fan-shaped and rectangular backboards (aside from the shape, obviously) is that the ball is not OOB if it passes over a fan-shaped backboard.

I have yet to find any reason for this rule, BTW. Does anybody know why this difference exists?

It's legal for the ball to pass by the <b>side</b> of a rectangular board, but not over the top. On a fan-shaped board though, you can't tell where the sides and top meet or end. Iow, you can't equally apply the same rules logic to both boards. That's why there's no restrictions on a fan-shaped board.