The most popular type of angle stop water supply valve is the compression type to connect to 1/2" copper pipe. These shut-off valves are used for bathroom faucets, vanities, kitchen sinks, toilets, and more. The come in both multi-turn and 1/4 turn type. These valves are most commonly found at plumbing supply houses and Home Depot and Lowe's. Many times it is confusing on which angle stop valves to buy, as they come in many different types. There are over 30 varieties in stock at Home Depot alone, so it is possible for one to purchase the wrong valve for their setup. Most commonly, 1/2" copper is coming out of the wall, and a 3/8" hose fitting is attached to the top. By using a lubricant oil like WD-40 between the compression ferrule and the copper pipe and valve, it is much easier to tighten the nut and get good compression with less effort. This not only allows a tighter fit, but can prevent over-tightening which is common with these types of compression fittings. Over-tightening will deform the copper pipe and not only cause a leak but ruin the copper pipe and it will need to be replaced before a new angle stop valve can be installed.