Guidelines for Notches and Cutouts:
To provide you with notches and cutouts, the corners must have fillets. A fillet is a rounded corner of which the straight edge emerges. The radius of the fillet must be equal to or greater than the thickness of the glass, but not less than 1/2".
All fabricated glass products with holes, notches and cutouts must incorporate tempered or heat-strengthened. Due to stresses created in the glass with these cutouts, annealed glass products are not appropriate. In addition, the guidelines below also apply for notch and cutout requirements:
The depth or width of the notch or cutout can not have a dimension larger than 1/3 of the narrowest dimension of the lite.
The leg length must be more than the depth of the notch.
The leg length must be at least 3".
The depth of the notch must be less than the width.
The inside corner(s) must have a radius equal to, or greater than the thickness of the glass, but not less then 1/2".