A set groups items that belong together — a coin series, a card checklist, a tool kit — and shows how complete it is ("12 of 20") and what it is worth together.
- Create — Holdings → More actions → Sets… → New set. Give it a name and, optionally, How many make it complete.
- Add items — select them in Holdings and choose Add to set…, or use More → Add to a set… on an item's page.
- Open a set — from Sets…, to see its members, remove one, edit or delete it.
An item can be in several sets, and its page lists them. A set has no value of its own — its value is its members' — so nothing is counted twice. Deleting a set leaves its items in the catalog.