A latch is a piece of hardware that keeps a door or a box closed.
The latch on the shed has a lock on it.
The latch on the toolbox is open.
In order to carry the toolbox, you have to close both of the latches.
The latch on a kitchen cabinet keeps the cabinet door closed.
When the word "latch" is used as a verb, it means that something or someone is very close, holding on, or sucking. The preposition "on" is usually used with "latch" to form the verb phrase, "latch on."
The little boy latched on to his mother’s neck and would not let go.
A leech will latch on to your skin when it’s underwater and suck blood out of your body.
A baby latches on to his mother’s breast for milk.
Dan in an unpaid intern at a radio station. He’s trying to latch on to a job as an announcer.