If you don't have a long bench but need to work on the edge of long boards, here's a trick (or what the computer-semi-literate call a “hack”). I have a good iron tail vise on the end of my short but heavy bench. This works well for the typical work I do and the space I have to do it in. The photo shows how I handle workpieces too long to rest on the bench lengthwise.
Sometimes for security's sake I'll affix a C-clamp or F-clamp onto the scrap* board right above where it passes through the top of the Workmate. That way, if for some reason the Workmate vise lets the scrap slip downward, the clamp will clog the opening and keep the scrap at the elevation I want.
Notice that using the Workmate this way takes advantage of its rigidity along the vertical axis. If you figured out a way to grasp the workpiece directly between the Workmate's top's halves, you would then find the setup was wobbly, as the Workmate flexes quite readily along its long axis. “Wet noodle” is a good descriptor for this longways flopsitude.
Also notice that you don't have to use a Workmate for this trick. An adjustable roller stand will work, as will a sawhorse or a couple of my bench risers with a block or two clamped on top. What matters is coming up with an outrigger support of adjustable height using materials you already have in the shop.
This idea is not earth-shattering, but it shows what you can do with a little ingenuity. Not all of us can have a massive workbench that clamps any workpiece we throw at it, in any orientation, with absolute rigidity; nor do we all get to work at our home workbench all day every day. Seeing new ways to hold the workpiece where you want it makes for quicker, more efficient, more accurate work.
Speaking of workbenches and workholding, next weekend is my “Build a Workbench in a Weekend” class at Highland Woodworking. As of this writing (Saturday night) the class has one opening. I also plan to build a bench myself during that class, and it will be available for sale - - see the “For Sale” sidebar on this site.
* “Scrap” is simply a convenient term for “extra, leftover, or otherwise uncommitted piece of wood lying easily at hand.”