I'm always impressed by the craftsmanship of the Hammond organ company. Here is how they handled the grill cloth at the corners of a speaker baffle. There are slots cut at each corner and the cloth is stuffed into them - rather than folding it over itself - which generally creates a thick build up of cloth. They also used brass plated staples, after the cloth was glued to the baffle. Not sure what type of glue. It's hard and clear yellow. Might be wood glue, or even hide glue.