Sometimes, especially in custom or race applications, spark-plug wires do not come complete and must be cut to size and assembled. These wires are usually of very high quality and will provide the best spark for your engine. Assembling them is generally not very difficult.
Measure each wire and cut it so that it fits exactly from the distributor to the spark-plug location. One good way to do this is to place one end of the wire near the distributor and the other to the spark plug you wish to connect it to. Mark the spark-plug end of it with a marker or pen, and then strip it using wire strippers. The reason for using wire strippers is that approximately ½ inch of the inner wire should remain sticking out of the sheathing. Label each wire to the corresponding cylinder if you are not going to assemble each one, and place it as you go so you know where it attaches.
Bend the inner wire (the part that is sticking out after the sheathing was stripped) over the outside of the wire and slip the copper attachment over the sheathing, trapping the inner wire on the outside of the rubber. Then squeeze the attachment with a pair of pliers so that it physically grabs onto the outside of the wire. Do not squeeze to the point that the rubber is punctured or damaged; you only need enough so that it grabs. Once the ends are crimped in this manner, slip on the rubber boots if applicable.
Test the wires to ensure they were assembled correctly. There are two ways to do this. The first way is to test them for continuity using an electrical multimeter. If you do not have access to this tool, attach the wire on the distributor side and hold the spark-plug end with shielded pliers. Start the engine and hold the spark-plug end of the wire near the valve cover or exhaust manifold and watch for a blue/white arc that looks like a tiny lightning bolt. If it is present, the wire is working properly. If not, inspect the connections on both ends of the wire.
