Depends on which left or right you're looking at, from the breech, or from the muzzle, I guess. I have a couple of period muzzleloaders from the 1840-1860 era, and both of them have wedges inserted from the left, looking forward from the breech. As mentioned, if you're right-handed, that puts the smooth part on the side of the forearm where the palm of the hand grips it.