Wildfield Borderpost — ruling 1

Casting this card by paying its alternative cost doesn't change when you can cast it. You can cast it only at the normal time you could cast an artifact spell. It also doesn't change the spell's mana cost or mana value. The only difference is the cost you actually pay.

Wildfield Borderpost — ruling 2

Effects that increase or reduce the cost to cast this card will apply to whichever cost you chose to pay.

Wildfield Borderpost — ruling 3

To satisfy the alternative cost, you may return any basic land you control to its owner's hand, regardless of that land's subtype or whether it's tapped.

Wildfield Borderpost — ruling 4

As you cast a spell, you get a chance to activate mana abilities before you pay that spell's costs. Therefore, you may tap a basic land for mana, then both spend that mana and return that land to your hand to pay this card's alternative cost. (Of course, you can return a different basic land instead.)

Wildfield Borderpost : règles, fonctionnement et interactions (MTG)

Wildfield Borderpost is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

You may pay and return a basic land you control to its owner's hand rather than pay this spell's mana cost. This artifact enters tapped. : Add or .

How it works : Wildfield Borderpost

Original English text — Wizards of the Coast / Scryfall

#1May 1, 2009· Wizards of the Coast
Casting this card by paying its alternative cost doesn't change when you can cast it. You can cast it only at the normal time you could cast an artifact spell. It also doesn't change the spell's mana cost or mana value. The only difference is the cost you actually pay.
No other card is named in this ruling.
#2May 1, 2009· Wizards of the Coast
Effects that increase or reduce the cost to cast this card will apply to whichever cost you chose to pay.
No other card is named in this ruling.
#3May 1, 2009· Wizards of the Coast
To satisfy the alternative cost, you may return any basic land you control to its owner's hand, regardless of that land's subtype or whether it's tapped.
No other card is named in this ruling.
#4May 1, 2009· Wizards of the Coast
As you cast a spell, you get a chance to activate mana abilities before you pay that spell's costs. Therefore, you may tap a basic land for mana, then both spend that mana and return that land to your hand to pay this card's alternative cost. (Of course, you can return a different basic land instead.)
No other card is named in this ruling.