What good is the straw

Hint 1 of 4:

It is one way out of the room.

Hint 2 of 4:

Horses like it. Look out the windows; see the horse ?

Hint 3 of 4:

OPEN RIGHT WINDOW and DROP HAY. Be sure you use the RIGHT window.

Hint 4 of 4:

The cart is now below the left window, so GO OUT LEFT WINDOW.