replacement glass

hello and thanks to all that answer!

I need to replace a glass panel in a pvc door, sorry but i can't take a photo so i hope i give enough info! i bought the house with it boarded up. its the type were you fit the rubber seals from inside which seem to be present.

I have contacted a local supplier who will make a panel to fit.

my questions

1) Do I measure the exact size of the opening and hope the glass supplier gets it spot on,or should i leave some tolerance? whats normal?

2) Is the double glazed unit a standard thickness or do i need to measure the recess minus the size of the seals?

hope these make sense if not just ask and i'll try harder!!

why not ask the people supplying it what they want / need to know?

That way you are g'teed to get the right answer

Will be calling on monday with the measurements but as i'm not at the property, a friend is going to measure so wanted to give him as much info as possible. If there are no other comments to this topic will just measure the opening and ask them on the phone. thanks