'Bevels' are basically half-cap/arches; the non-inverse ones make rounded edges, while the inverse ones make things like cornices and corners. They come in both patch and brush-vased versions, and work almost the same as caps and arches, so look at those now if you haven't already.

Bevels are currently introduced on both the Curves and Brush Curve RMB menus for polys, just like arch & cap. Presently there are two types that can be introduced direction, Left Corner and Right Corner; then varieties can be created by setting specifics. The Left corner curves from the left side of the guide-brush to the back, the Right corner from the right side of the brush to the back.

For different orientations there's lower and standup specifics (the latter instead of onside), also inverse and thick (presently only patch-based). There's also subdivide, to control the quality of the circle-approximation, and inner for brush-arches.

Texturing is similar to arches; the texture on the curve is projected from the back face, and onto the top and bottom 'flanges' from the top and bottom faces. In particular, suppose you want to align a texture on the bevel to make a smooth curve walls forming a corner?

First, fit a brush into the corner, and then, looking along a wall intothe corner, make the brush left or right bevel as appropriate. Next, tag one of the wall-faces, and wrap texture from tagged onto the other wall. Then RMB on the back face of the bevel-builder (the face whose name is back), and texture|wrapping|from tagged mirror. (And if it's patch-based, don't forget to caulk!)