Fix for a damaged cord
Accidentally cut your good, heavy-duty extension cord? Replacement cords are expensive, and you can save money by just repairing it.
Technically, you’re not supposed to splice extension cords. Even if you solder the wires, wrap each wire with electrical tape and encase the whole splice in heat shrinkable tubing, it still won’t have the abrasion resistance of a new cord. Plus, it’s not permissible under the National Electrical Code.
Instead, if both sections are long enough to be worth saving, just buy a high-quality plug and receptacle and make two cords out of one. Be sure the new ends are rated to carry the same load as the old cord and that both have built-in strain relief clamps. Otherwise, just buy one end and accept the fact that your 100-ft. cord is now only 92.56 ft.