Fortify

From MTG Salvation Wiki

Fortify is an ability that appears on Fortifications. It's exactly the same as equip, except that it affects a land instead of a creature. Fortify was introduced in Future Sight.

From the Comprehensive Rules: 502.65. Fortify 502.65a Fortify is an activated ability of Fortification cards. "Fortify [cost]" means "[Cost]: Attach this Fortification to target land you control. Play this ability only any time you could play a sorcery." 502.65b For more information about Fortifications, see rule 212.2, "Artifacts." 502.65c If a Fortification has multiple instances of fortify, any of its fortify abilities may be used.