Quarter round
A quarter round is a convex molding whose cross section is a quarter circle. It is one form of ovolo. A variation is a base shoe, a quarter of an ellipse. Most quarter round is of small gauge and relatively flexible. It is typically used as a decorative build-up element in mantels and other architectural features, and at the lower edge of baseboard to hide any gaps between it and a floor. Base shoe is used similarly in flooring applications. Quarter round is produced in hardwood, softwood, engineered wood, and extruded plastic. References

Floors
Architectural elements