Interchangeable cores (IC) are a convenient way to be able to switch out locks without having to dismantle the entire door handle or lockset. They allow someone with a special key called the “control key” to quickly remove the lock and replace it with another one.

The way that it works is the control key. The control key is a special key, which doesn’t actually open the door at all. Its only purpose is to remove the interchangeable core so that it can be rekeyed or replaced. A simple turn releases the core from the housing, which is the interface between the core and the door. When an interchangeable core is inserted into a housing, it is mechanically locked into place and cannot be removed except by using the control key.

Those are the basics, but of course with anything lock-related, things get complicated when you start to get specific about the brand of lock that you want. Interchangeable cores were invented by Best Access Systems back in the day and since then everyone has jumped on board. They’re just so convenient, all the lock makers wanted a piece of the pie: Schlage, Corbin-Russwin, Ilco, Yale, Arrow, and so on.

If possible, your best option is to request your door vendor to provide housings to accept Small Format Interchangeable Cores, which they can pre-install so when the job’s done you can simply go around and put in the cores with the control key. In some cases the core can be installed directly into the handle without a housing, which is even easier.
If that’s not possible, you will need to order the housings yourself, which is not too hard. You just need to know two things: First, is the door using a locking pull or a mortise lockset? Pulls will need a Rim Housing, which has a long tail on the end to pass through the pull to the thumb turn on the inside. Second, if you have a mortise lockset, you’ll need to know which type of cam to use for the Mortise Housing. This really depends on the brand of lockset that you have. There are a few different common types, and an easy rule of thumb is to order the cam from the same brand as your lockset.
If Interchangeable Cores still leave you scratching your head, leave your question in the comments or email us at locks@openlocks.com, we’ll be glad to answer it.