Crude Rampart
Creature — Wall
Defender (This creature can't attack.)
Morph 
(You may cast this card face down as a 2/2 creature for . Turn it face up any time for its morph cost.)
Success is one part inspiration, nine parts desperation.
Sam Wood
Onslaught (ONS)
• #17Rulings
If it attacks while face down and is turned face up during combat, this will not remove it from combat.
(wotc • 2004-10-04)
Rulings
If it attacks while face down and is turned face up during combat, this will not remove it from combat.
(wotc • 2004-10-04)