Quick Question regarding temp thermostat

I am installing a new thermostat in my 75 /6 Duster. One quick question.... is the thermostat locked into place by the gasket (insert thermostat, then gasket, then outside piece and tubing) or loose from gasket ( place gasket, insert thermostat, ect... ect..) Need a quick response so I can refill her with antifreeze! Thanks

Never mind... I guess I have it figured out. I didn't know because I believe it was the original thermostat and couldn't tell how it went on because the gasket was soooo worn.