Anchor

The Anchor is a special item in Super Mario Bros. 3 that is found in Desert Land, Giant Land, and Ice Land. As the airship typically moves to a random location if Mario and Luigi fail to conquer it on the first try, the Anchor will prevent this from happening, holding the Airship in place.

Locations
The Airship is a rare item, which can only be acquired inside of White Toad Houses in even-numbered worlds. To unlock the White Toad House, you must collect a certain amount of coins in certain levels: Here are the levels and the amount of coins needed to access the White Toad House and collect the Anchor:
 * Desert Land (Level 2): 30 Coins
 * Giant Land (Level 2): 22 Coins
 * Ice Land (Level 7): 78 Coins