Board Thread:Questions and Answers/@comment-32306613-20170616162304/@comment-26155909-20170617082954

It's an option that protect your ships from being scrapped or used for modernisation.

In the page where you select a ship to add in your fleet, if you click at the right of the ships line a heartlock will appear/disappear.

Here's an exemple of what i looks like:

In the exemple, nagato is not locked but the others are.

There is basically the same feature for equipments.