Hello, this is Tyler with Appliance Service by Paul located in Salt Lake City, Utah. We're going to walk you through the proper steps of how to fix a knob on your gas stove. Now, one of the first things you need to look for on your oven knob if it's loose or won't stay on, a lot of oven knobs, once you pull it off will have a little metal insert inside of the knob. If that metal insert is missing, the knob won't turn, won't grab and won't turn your oven on. Also if that metal insert is missing then the plastic around the knob can be cracked. Now there is no repair for this. You have to order a new knob or in some cases you can order a new metal insert to go inside of your knob. In some cases, the shaft of your actual burner switch will be broken and if that's the case you need to replace the burner switch. If the shaft is okay, get your new knob or get the metal insert and insert it into your old knob and it should go right back on. Now if for some reason you need to replace the selector switch inside of here because your knob is okay, what you need to do is remove these two screws and then from the back you'll remove the wires off the switch and then replace the wires on to the new switch, reattach the two screws and the knob goes right back on. Again, this is Tyler with Appliance Service by Paul. We've just walked you through the proper steps of how to fix your knob on a gas stove.