Due to the harsh winter we just endured, we lost our greenhouse film and the frame tilted at the north and south walls a full 7 inches off being a proper straight 90 degrees. Before putting up new film, we straightened out the frame by tying a rope around the apex of the North wall and pulling it back to 90 degrees using a CAT and a level. Before setting the frame free from the cat, we drilled four braces in place, two on the east long wall and two on the west long wall. With each brace making an 90 degree arrow pointed toward the middle of each long wall, the frame became sturdier as the energy was being evenly distributed through the entire structure. Its all physics, people.
This picture better demonstrates what I am talking about:
One brace is clearly visible up front and center. This brace is on the third bay on the right end on the east length of the greenhouse, the second brace is on the the third bay on the left end of the east length of the greenhouse. The same is of the two braces on the west length. The braces point towards each other: > < pointing the energy in, keeping the greenhouse North and South wall up straight and tall.