1.) Just as there is a high probability you can steal a card from another user’s pack as long as yours is of a similar or higher value, other players can steal unprotected cards from your Pack, assuming they have been given steal permission (as a co-op player), or if you and the other player both play Free For All (FFA). In order to prevent this from happening, there are a few ways you can securely “lock” a card in your pack.
2.) Any card that has just been stolen or purchased with credits has a temporary, fifteen minute lock placed on it (the purple clock in the top left of the card) to protect it in case you’d like to lock it permanently; hovering your cursor over the card will show you when the protection ceases.
3.) Cards that have been acquired through trade are safe for 24 hours in your Pack.
4.) Cards that have been purchased or won using tickets are automatically and permanently locked when in your Pack. These cards will have a green leaf icon in the top left corner (which will disappear when the card is vaulted). In the picture below, the 'Radiant Reba' card is always safe from being stolen since it was bought with tickets:
5.) If a card in your Pack is only temporarily protected, you can purchase a lock gadget (including a Pack Pet lock) from the markets to add to a card and prevent it from being stolen. Free users can have up to 5 locked cards in their Pack at one time, while premium users can have up to 15 locked at once. A card with a Pack Pet lock does not count toward this limit.
6.) You can purchase locks from three different markets:
-Santa Monica: any player can purchase a lock from here for credits
-Las Vegas: any player can purchase a lock from here for tickets
-Alcatraz: XL players can purchase a lock from here for credits:
7.) When you find a lock, click on it to purchase. It will automatically move to your Pack.
8.) Now that the lock is in your pack, click on the lock, and then click 'Use Gadget' to activate it:
9.) Click the card you would like to protect with the lock. Note that you are unable to lock leafed cards that are permanently safe already, cards that have already been locked, or any Pack Pets, so they will be greyed out when you select a card to lock.
10.) Click Apply. The card will automatically return to your Pack with a lock icon in the top left corner. It is now permanently safe in your Pack: