A base for a fence post is a foundation that supports and anchors the post securely in the ground. It can be made of concrete, which is poured into a hole around the post and allowed to set, or from pre-cast concrete blocks that are set around the post and mortared together. A base provides stability, prevents the post from heaving or shifting in the ground, and protects it from rot or decay caused by moisture. It is an essential component for ensuring the longevity and integrity of a fence.