When you're looking to switch up the key to your locks, you'll need to purchase a key change kit that is tailored to your brand of knob, lever, or bolt. These kits enable you to alter the key on a lock to match the existing keys in the kit. You'll usually receive between three and six keys that are all cut identically. There are two types of kits available: those designed to change the key of some padlocks for a specific key included in the kit, and larger kits that will allow you to freely change the key to your locks with any old key.
In order to open the lock with a different existing key, for example, and no longer use separate keys for the front, rear, and side doors, the lock must be disassembled and the pins, which are of different heights, removed and replaced with new ones that match the cuts and grooves of the new key. If you make a mistake while doing this, pins and springs may fly out everywhere, and a local locksmith will charge more to put it back together. To check if they are from the same key holder, take the key you want to use and check if it enters through the hole in the new lock. For a wrench to rotate the locking mechanism, the configuration of the pins must match the depth of that key's unique slots.
If the key doesn't slide in, then it is likely that the cylinders (keys) are different and the lock cannot work with that key. When you shop at a locksmith or hardware store, they will often change the key on the locks to match another existing key at no cost. To save money, always take them to a lock store and don't install them (so the locksmith doesn't have to go to your location).