The Own contacts only limit used to be all or nothing. When somebody went on holiday, the only way out was to lift the restriction and open the entire database with it. A share is the middle ground: one pair of people, one direction, revocable at any time.
What you need it for
Where it lives
Settings · Tools · DB-Leads · Shares. The area requires the Share other people's contacts permission, and it requires it for viewing too: the overview answers the question "who sees whose customer data", and that on its own is information about how your office is organised.
Pick the people
Two dropdowns at the top: the person who may additionally see, and the person whose contacts become visible. Read it as a sentence: "Anna sees Bernd's contacts."
Add a note
Optional, but worth it. A share without a reason cannot be judged six months later, and by then nobody dares remove it. "Cover until end of October" is enough.
Grant it
It takes effect immediately, with no need for anybody to sign in again.
Each row is revoked individually via Revoke. That takes effect immediately as well.
What a share is not
It is directional. "Anna sees Bernd's contacts" does not mean Bernd sees Anna's. If the two cover for each other, you need two shares.
It hangs off the assignment, not off the individual finding. What is shared is what Bernd looks after, not finding 4711. A finding appears and disappears with every scan; a share tied to one would be a list of dead references within a week. When a contact changes assignee, it moves along with the assignment.
It survives a change of administration. If the person who granted the share leaves the office, the share stays. Otherwise the next offboarding would silently cost half a team its access.
When nobody is restricted
Then a share does nothing, because everybody sees everything anyway. The area says so rather than offering a setting that has no effect. A share only becomes effective once at least one role or person carries the Own contacts only restriction.
What gets recorded
Every share granted and every share revoked lands in the workspace audit log, with both people involved. A share moves who sees whose customer data; whoever reviews that later needs both sides. The note is not in the log, it stays on the row itself.