Our tempered glass backboards come with steel spacers and a foam pad and these are used to separate the rim from the glass backboard and prevent the backboard from shattering.
You should have 1/8 to ¼ inch gap between the backboard and rim when properly installed. These components must be in position BEFORE attaching the yokes and assembling the rim. If the spacers are not in place, the board can be prone to shattering given it is a glass backboard.
Please do not overtighten the bolts, as this can also lead to the board shattering upon installation.