A bracket system for forming gate assemblies comprising at least two brace members that are rigidly attached to hinge assemblies. The brace members are adapted to be attached to support members to form two corners of a gate box functioning as the structural portion of the gate assembly. The hinge assemblies are adapted to be rigidly attached to a fence post to allow the gate assembly to pivot relative to the fence post. Gate assemblies of arbitrary height and width can be formed using the bracket system.