Jim, it really depends on the project. I use 1/4" Masonite(tempered hardboard) for most of my templates. A production template needs to be built of sturdier material. I designed this rail system for one of the forum members so he could mass produce clock bodies. There are individual sleds that ride on the rails with different patterns cut in them. Each sled is designed to work with specific guide bushings and router bits. (There are more than the three sleds shown) The sleds are located in different positions using the key to lock them in place. After sled 1 has been used in each position sled 2 replaces it and so on. This greatly reduces bit changes and speeds the process.
I only designed this system, Ron did the layout and build; he did a great job! The last two photos show the finished product. The bench top shown is actually part of the jig; more materials here than a typical template but it is all the same idea.
"Living in the D" (this means Detroit!)
"It's fine to disagree with other members as long as you respect their opinions"