95 DT thermostat question

Changed various cooling bits but have a leak on the thermostat and reading RAV should there be one or two o-rings involved in keeping the water in? When I took it apart 1 o-ring came out which seems way too big to fit the thermostat itself. I have made an o-ring from two (with super glue) to fit on the rebate/flange of the thermostat and then placed the nasty large old one over this to form a seal between the thermostat housing and the front of the engine. I have ordered another new thermostat with an o-ring but am still a little confused about the correct positioning of them. If any body can help me understand this thanks......