If you have 3/4” bench dog holes on your bench and a couple of handscrew clamps then in 10 minutes you can merge the two into a very flexible and powerful clamping system that works with small boards, long boards and even irregular pieces. I’ll let the photos tell the story … and keep in mind, the modification to the handscrew does not prevent you from using it as an ordinary handscrew too. I use them on my workbench and my sawbenches.
Clicking on any of the photos will take you to the more detailed explanation.
There are only three real considerations:
1) The hole you drill for the peg should be plumb, so use a drill press if you can.
2) Oak or other hardwood dowel is better than poplar or other soft wood.
3) Regarding the size of the handscrew. Larger handscrews limit how close they can work together, but smaller handscrews limit the maximium opening of the jaws. I like the 6 or 8” handscrews but size them based on your needs.
-- Galootish log blog, http://www.timberframe-tools.com