A corner rounder quite literally rounds off severe corners of rectilinear pages by cutting them with a device similar to a hole punch. This craft accessory is used in fiber arts and scrapbooking to make ordinary, square corners softly rounded and more attractive.
Gift tags, photographs, mountings, cards, mattes, and leaves of paper all benefit from rounded corners. This deliberate treatment of specialty papers makes scrapbooks, collages, memory books, and photo albums even more special. One might use a corner rounder on a portrait to make it resemble old-fashioned prints, or on the heavy cardstock of a sticker book so children don't cut their fingers on sharp edges. You can easily make bookmarks, sticker labels, or party invitations with this convenient gadget for hobbyists.
The blade in a corner rounder can be curved to various degrees to achieve various effects. A standard, small rounder might use a 1/2-inch (1.25 cm) circular radius for any size of paper. But certain types of corner rounders can switch between blades, from a subtle 1/4-inch (.63 cm) radius to a deeper 1-inch (2.5 cm) curve. Some blades are fixed with decorative lines, to turn corners into hearts, scallops, or notched slopes.
A hobbyist might use a simple, plastic, hand-held corner rounder that cuts a single medium-weight sheet at a time with an enclosed curved blade. These types of rounders do not have a container that collects the scraps of corners, but usually ejects them immediately after they are hand-punched. There are also versions of a professional, desktop corner rounder designed to handle many pages simultaneously. These often have a trap to hold the paper waste that can be emptied like the bottom of a hole punch. Such commercial corner rounders are often used to round the corners of batches of business cards or postcards.
A corner rounder can even be electric, so that when you insert a page, the machine punches it for you, for high volume jobs. Any home office or crafter's studio would benefit from one of these nifty tools.