Hook-up wires are a type of electrical wire that is used to connect electronic components. They are available in two types: solid and stranded. Solid hook-up wires are made of a single, solid core of copper. They are more rigid than stranded wires, and they are better suited for applications where the wire will be subjected to a lot of bending or flexing. Stranded hook-up wires are made of a bundle of copper strands. They are more flexible than solid wires, and they are better suited for applications where the wire will be subjected to a lot of vibration or shock.