The end caps are secured to the top with dovetailed keys screwed to the ends of the top. Use a dead blow mallet to drive the end cap in place.

 

I have used dovetail keys screwed to the sides of a case to attach molding for years. Properly fitted the keys hold the molding tightly in place while allowing for seasonal wood movement. The same technique scaled up works for larger pieces of wood, like the end caps on one of my benches, as well. The keys short length, 4 to 4-1/2 inches, keeps the distance between the screws to a minimum, and reduces the chance of cracking the top as it shrinks and swells. The end cap is screwed to the top with a single lag bolt at the front of the bench. I use this adaptation of the sliding dovetail to attach the end caps on every bench I have built over the years. The row of wedges fitting snuggly in the dovetailed groove milled in the end cap also helps keep the bench top flat.

 

For more information about building a wooden tail-vise, the fixed jaw with dog-holes, and the installation of the end caps which support both, read my article in American Woodwork magazine, titled "Wooden Tail-vise," October-November 2011, #156. If you can't locate a copy, email me and I will mail you a photocopy of the article. The article has all the construction drawings and dimensional details that I don't think are appropriate for a short blog post.