The business end of the stichaxt is more or less a giant chisel. It is single beveled, and the direction of the handle determines how the tool is handed. If the handle goes off to the right, then it is right handed. The angle of the bevel is about the same as that of my framing chisel.
Mine is a bit over 17 1/2 inches long, and about 5" wide at the handle. It is 1 3/4 inches in the body.
The back may or may not be slightly convex, depending on who makes it.
I need to make one correction to my previous post concerning how to use it.
The correct posture is not simply kneeling, but rather kneeling with one knee resting on the timber being cut and the other extended out to the side. The timber needs to be at the proper height so that this is comfortable. The top of the timber might be about the height of a chair.
You should always have the timber turned so that you are cutting down when using the stichaxt. You can cut horizontally, but it works better to always cut down.
Here are some pics that may help clarify things for you.

First a size comparison, next to a 1 1/2" framing chisel
notice the beveled sides, which help the tool to cut more efficiently.
and a closeup of the business end so you can see the bevel
hope this answers your questions, Tim