A Weapon Repair Kit repairs allows you to repair any weapon in the game. The amount you repair the item depends on your Repair skill.
This is one of the most useful items in the game because rare items are difficult to repair yourself, even with the Jury Rigging Perk. With rare and expensive items, repairs often require identical items, so unique items are impossible to repair without paying for a repair or using Weapon Repair Kits.
 Making Weapon Repair Kits
You can craft Weapon Repair Kits using a Workbench as long as you have a repair skill of 50 or more.
These kits use incredibly common components that you find lying around throughout the game, making this item not only very useful, but very easy to create. Players who have the skill to craft these items
 Required Materials
Many of the above items can be purchased from Gibson's Scrap Yard, and Gun Runners and are easy to get to because you can quick travel directly to each location. Mick & Ralph's sells Duct Tape, and Wrench, and can be reached by quick travelling to the Freeside East Gate
The hardest materials to get are the Duct Tape and Scrap Electronics, which are not prospected easily, so buy those from each of the above 3 places as they become available and keep them handy in your inventory.
If you don't travel with Veronica as your companion, the easiest place to put together the materials is the Workbench in Goodsprings, because the workbench is right near your front-left when you fast travel there (beside the General Good store).
 Making Money Using Weapon Repair Kits
As you already know, selling items to merchants is the primary means of generating caps in Fallout. Your Barter skill and the condition of the item you have determines how much you receive for items. When you get to higher levels using a Weapon Repair kit can increase the value of your item significantly (sometimes 500 caps or more), yet the items used to craft the Repair Kit are worth only a few caps at most. This is a huge way to leverage a few caps into thousands.
- Memorize the items required to make Weapon Repair Kits
- Buy weapon repair kits whenever you see them
- When you find expensive weapons in low condition, do NOT repair them with other items of similar value! Instead, use Weapon Repair Kits on EACH item, which will increase your profit several fold
- Eg You find 2 poor condition Sniper Rifles, instead of repairing one into the other and then selling a single good condition Sniper Rifle, use Weapon Repair Kits on each rifle and sell 2 good condition Rifles. The cost will be less than 50 caps in materials but you will easily profit 2000 caps.