We are going to hire somebody to replace our sliding glass patio door. Its a standard sliding glass patio door, similar looking to this:
I am going to buy the replacement door at auction, but first I need to know exactly what size door I need. I searched how to measure this online, but there appears to be contradictory advice on what the proper way to measure a patio door is.
Is there a proper way to measure the size door I need without removing the existing door first? Please include pictures if possible and define your terms if they are not terms a layman could understand.