The hinge needs to be opened quite wide so the pawl on the side of the hinge nearer the top of the door that is holding it in the locked position is released and drops down to hold the hinge open. Procedure: place oven door flat on a table with the hinge face up, but overhanging the table edge a few inches. Use a screwdriver that fits though the hole in the hinge, and push it right through to the hilt. Use a pair of long handled adjustable pliers to grip the shaft of the screwdriver immediately the other side of the hole from the hilt, holding the hilt tight against the hinge. The rounded portion of the head of the pliers should rest on the bottom of the oven door (place a cloth underneath the pliers so they won't scratch the door), and the handle will point upwards. Making sure you have a firm grip, rotate the pliers downwards towards the bottom of the door, which will open the hinge. You will need to rotate quite some way before the pawl is released to lock the hinge open - you need the overhang to do that. Once the hinge has locked open, release the pliers and remove the screwdriver. Repeat for the other hinge if needed.
Mark, July 2012