The ?" Sure Fit Rubber Tiles appear to come with no corner or edge pieces. Rather, they seem to come only as interlocking pieces or straight pieces. Is this correct?

Yes, our 3/8" Sure Fit Rubber Tiles don't come as corner or border tiles. To create a corner or border piece with our interlocking tiles, you would need to cut the tabs off the tiles to create them. For the straight-edged version, you can just cut the tiles in place to fit your room. Cutting our rubber tiles is very easy with a sharp utility knife and a straight edge.