This iron-banded drawbridge resizes to fit the portal it's placed in, then raises or lowers with a single word.
Wondrous Item 17,000 gp
You can command this drawbridge to raise or lower as a free action. You must be able to see the drawbridge to activate it, and it neither rises if any creature is on it nor lowers if any creature is under it.
Published in Adventurer's Vault 2, page(s) 81.