Found a Key Component for New Field Easel

I'd been looking for these quite a while. The main problem was I didn't know the name of the pieces of hardware I was looking for. It's really hard to find something that you don't know the name on the internet.

I went back to one of information seeking principal I've learned at the graduate school; (Ahem!) find a person who knows what you're looking for. I simply went to a near-by home depot and asked an associate with a sample from my studio easel. In less than a couple of minutes, the associate showed me where they are.

They're called as thumb screws and insert nuts. With these pieces of hardware, the sliding piece of wood can press down a stretched canvas and hold it tightly.
My next step is to design&draw the canvas holder including the sliding mechanism.