Fortify

Fortify is a keyword ability that appears on Fortifications. It's exactly the same as equip, except that it affects a land instead of a creature.

History
Fortify was introduced in Future Sight. It has only been printed on one card so far, the timeshifted Darksteel Garrison. Mark Rosewater has considered the mechanic difficult to implement, as the typical sanctity of lands limits both the utility of re-usability that equipment hold, and the ability to put powerful effects on fortifications.

Rulings

 * If Darksteel Garrison and the fortified land would be destroyed at the same time, only Darksteel Garrison is destroyed.
 * The second ability triggers whenever the fortified land becomes tapped, not just when it's tapped for mana.
 * The triggered ability is mandatory. If you don't have a creature to target, you must target another player's creature, if possible.