axle guard

from The Century Dictionary.

• noun Those parts of a railroad-car in which the axle-box plays vertically under the yield and reaction of the car-springs.

from the GNU version of the Collaborative International Dictionary of English.

• The part of the framing of a railway car or truck, by which an axle box is held laterally, and in which it may move vertically; -- also called a jaw in the United States, and a housing in England.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The part of the framing of a railway car or truck, by which an axle box is held laterally, and in which it may move vertically.