Plate casters have a mounting style that uses a flat plate, typically square with holes at each corner, which is meant to line up with the mounting pattern found on an object. These holes form what is known as the bolt hole spacing (BHS), which is critical in mounting plate casters. Plates come in various styles and are meant for mounting to different objects, so it is important to ensure the bolt hole spacing on the plate caster is the same as the object it is being attached to. Sometimes plate casters are welded to the object, and in this case no bolt holes are necessary.
Stem casters have a mounting style that uses a single rod or stem protruding from the center to secure the caster to various objects. While plate casters are typically used for most medium- and heavy-duty applications, most common stem casters are for light-duty applications such as furniture and medical equipment. Stem casters can be mounted using a variety of methods such as threaded rods of all sizes which screw in, hollow kingpin casters which slide over a stud and can be bolted in place, and press-fit stems meant to snap into place securing the caster and cart together.