Try to help your toddler see sleep as a good thing. If you have given him ample opportunity, and yet he still has not taken a nap, then trust that he will sleep later. Even if he doesn't take a nap, he will probably benefit from a time of playing quietly. Make the house as quiet as you can and help him find some quitetime activities. This can provide some rest and a time for both of you to recharge.
Fresh air can work wonders.
Using violence or restraints or locked doors in order to keep a child in bed will most assuredly backfire and bring strife and sorrow to the heart of a child. If you are having troubles getting your child to sleep, you may wonder how I can write so calmly about this. She often takes naps. Our experiences are not the same every day, but I can see so clearly that my little girl is growing up. Enjoy your little ones while they are little.