By Kent · Lock Depot Staff Writer

Double cylinder means a key on both sides

Most commercial cylindrical locks have a keyed cylinder on the outside and a push button or turn on the inside. The Yale 4700LN double cylinder models put a key cylinder on the inside lever too. That one change is what makes them useful in rooms where the person inside needs to lock the door without going into the hall, or where the staff want control from both sides. It is also what makes them a code question, which we get to below.

Three double cylinder functions come up all the time: AU4718LN (Classroom Security), AU4721LN (Communicating) and AU4730LN (Utility or Institutional, the Asylum function). The catalog lists all three in the Augusta lever in Satin Chrome (626). They are genuine Accentra hardware, the commercial line formerly known as Yale, so a locksmith who still specs it as a Yale is looking at the right lock. The 4700LN is a Grade 1 heavy-duty cylindrical (bored) lockset built for schools, offices and healthcare corridors.

The three, in one list

• AU4718LN, Classroom Security. Per the catalog, it lets a teacher lock the outside lever from inside the room with a key, without opening the door into a threat. This is the lockdown-friendly classroom function.
• AU4721LN, Communicating. The catalog describes it as coordinating a pair of openings between adjoining rooms.
• AU4730LN, Asylum / Institutional. Both levers stay locked and key-operated on each side, for controlled, high-security rooms.

All three are priced the same in the catalog, so the choice is about the room, not the budget.

Which room gets which

A classroom where the teacher needs to lock from inside: 4718

The old answer was a classroom lock where the lock side was outside only. To secure the door during an emergency, the teacher stepped into the hall with a key. The classroom security function fixes that. The teacher locks the outside lever from inside the room with a key and stays in the room. Check your own code on what is allowed in your jurisdiction: the specifics vary, and that is a call for the school district's fire marshal and architect, not a hardware counter.

A pair of rooms that share a door: 4721

Communicating doors connect two rooms: a pair of offices, two exam rooms, a classroom and a prep room. The communicating function is built for that pair. The catalog language is short, so ask us if you need the exact function behavior for your door. We would rather confirm it than guess at it for you.

A room that needs both sides controlled: 4730

The institutional function keeps both levers fixed. A key is needed on each side to move the latch. Typical uses are rooms where you want to control who goes in and who goes out: a records room, a medication room, a secured utility space. The catalog's phrase is "controlled, high-security rooms." Be careful. A door that needs a key to leave is a life-safety problem on a normal means of egress. Do not put it on a door that is an exit path.

The egress trap with every double cylinder lock

Keyed from both sides means someone has to have a key to get out. In an emergency, that is the one thing you cannot count on. Building codes in most places restrict where a lock like this is allowed, and the rules differ by occupancy. If you are not sure, a double cylinder lock goes on a door the authority having jurisdiction has already approved for it. We cover the single cylinder version of the corridor and communicating classroom functions in this Yale 5400LN guide. Read it first if you are not sure you need double cylinder at all.

What the 4700LN is, and what it is not

The catalog calls the 4700LN a Grade 1 heavy-duty cylindrical lockset. Grade 1 is the top durability tier, which is why it is sold to schools and hospitals. The Augusta lever comes in satin chrome in the listings above, and the same family also runs in other finishes. The 4700LN is a cylindrical lock, which means a bored door prep, not a mortise pocket. If your door is cut for a mortise lock, you need a different family, like the Yale 8800 mortise. If you only need a service station function, see the 4706LN guide.

Before you order

1. Name the room and what happens inside it. The function follows from that, not from the part number.
2. Confirm the door is bored for a cylindrical lock.
3. Ask the building official whether a double cylinder lock is allowed on that opening.
4. Tell us your keyway if you want to match an existing system.

Common questions

What is a double cylinder cylindrical lock?

One with a key cylinder on both the outside and the inside lever. A key is needed on each side where the function calls for it.

Is Yale the same as Accentra?

Accentra is the commercial line formerly sold as Yale. The 4700LN is the same family the trade has long called a Yale.

What is the Classroom Security function?

It lets a teacher lock the outside lever from inside the room with a key, so the door does not have to be opened to lock it.

Can I use an Asylum function lock on an exit door?

Generally not. Both levers need a key, so someone inside cannot leave without one. Check with your building official before you spec one.

Is the 4700LN a Grade 1 lock?

Yes. The catalog lists it as a Grade 1 heavy-duty cylindrical lockset.

See the rest of the line on our Yale page. Tell us the room and we will confirm the function before you order.