On the Goalrilla Anchor System, should the nuts that hold the anchor plate be left on when the pole is installed?

Yes, these bolts are used if you need to make adjustments to the pole. With the pole resting on top of the nuts they can be turned so you can make sure the pole is plum. After making your adjustments tighten the top nuts securely to the plate against the lower nuts.

When adjusting my basketball system, the arms press against the glass on the backboard. How do I fix this?

The arms are assembled incorrectly. The arms should be flipped over to assemble in the shape of the letter "Y". Failure to do so could result in significant damage to your glass and void the warranty.

Table Tennis

How can I fit screw #19 into the U-Leg and U-Support?

Please refer to the video in the instruction videos list titled "How To Insert Screws into the U-Clip".

Stiga ST3000 (T8730) Table Tennis Table side to side adjustment