The key question is not what can I gain but what do I have to lose.

The key to raising every soldier into a great warrior is in strengthening training.

For code-type locks that don't need a key, there are 'free dial' systems where you can set any number you like, and fixed types where the number is set in advance.

Before meeting your guests, be sure to carefully check that the toilet door locks.

Fasten the gate.

I remember locking the door.

Remember to lock the door.

Don't fail to lock the door.

I forgot to lock the storeroom.

I left my key in my room.

I've locked myself out of the room.

The room was locked.

Please make sure that the door is locked.

She handed out a key to him.

She may have left her car key in her room.

She is looking for her car keys.

She had left the front door unlocked.

She put the key in her pocket.

She looked in her bag for the key of the house, but could not find it.

She was angry to find the door locked.