There is a wide variety of round gouges that can be used in relief carving. Since the round gouge is probably my main stay cutting and shaping tool my kit has, from left to right, a u-gouge (also called a veining tool), a small tight Japanese, a large tight Japanese, a large half-circle, a medium wide sweep, and a large wide sweep.
Round gouges can be tight, meaning that the curve of the cutting edge is about 1/3 of the diameter of a circle – these are the gouges that eat away wood during the rough out steps. Half-circle rounds are even tighter and make a wonderful scoop texture to your background work. The wide sweep cutting edge is very open, only a partial arch of the circle. The wide sweep is used to begin smoothing the background rough out work.
The u-gouge is perfect for those almost impossible places in your relief. The cutting edge is about or less than 1/8″ wide so it tucks nicely into just about any tight corner or space. The u-gouge in the Flex-Cut set that I use has a bent shaft which drops the cutting edge about 1/8″ down from the main tool shaft. That drop lets me glide the cutting edge along the background wood in a flatter, more prone position.
Any tool can be used up-ended in a push stroke cut. In very tight spaces I may not have room to get the point of my bench knife at the correct angle to cut free the gouge strokes. Instead I can up-end my u-gouge, or in the photo sample a v-gouge, even a straight chisel. Simply position the cutting edge at a 90 degree angle and push the cutting edge down into the wood. Up-ended v-gouges make perfect square corners.