which door glass will work on a convertible?

I tried going to a glass shop and the first question they asked was is the glass tempered and I said yes so, they said as soon as you would touch the glass with a drill the glass would shatter because it was tempered. I asked how do they drill holes in the glass than and he said they do it before they temper it. Basically what I was asking them to do was drill a hole in the glass and it was a no go. Thanks for the reply
Pat