The horizontal member beneath the studs in a framed building.

Electrode used in magnetrons and backward-wave oscillators to carry a current that generates a magnetic field in the direction wanted.

The lowest part of a valley.

1. The bottom of a sedimentary stratum.

2. The middle and lower portion of the shear surface of a landslide.

3. The underlying fault plane of a thrust nappe. Also known as sole plane.

The basal ice of a glacier, often dirty in appearance due to contained rock fragments.