What is the name of the vertical wood or metal member that is used to support horizontal elements in walls and partitions?

The term used to describe the vertical wood or metal member that supports horizontal elements in walls and partitions is "stud." In construction, studs are crucial framing components that create the structural framework for walls, providing support for the materials like drywall or plaster that cover the walls. They play an important role in distributing loads vertically and ensuring the stability of the wall structure.

In contrast, other terms listed refer to different structural elements. A post typically stands alone and supports beams or carries loads from above, but it is not specifically designed for wall framing like a stud is. A truss is a structural framework that is typically used to support roofs or bridges, made of triangular units, and therefore serves a different purpose than the vertical members in walls. Similarly, a ledger is a horizontal support member attached to a structure's wall, primarily used for deck framing and not as an independent vertical element. This distinguishes studs clearly as the correct answer in the context of wall and partition framing.