This is the back of the trim tab. Inside there are small ribs. These two attach to the control rod that moves the trim tab...a pretty important function. The yucky hole top right is the result of a 3X rivet gun. This gun allows adjustment of the pounding action of the gun from a gentle tap to an explosive force that could move a mountain. I think it's what John Henry was up against when he 'died with a hammer in his hand, Lord Lord, he died with a hammer in his hand." Anyway, it inadvertently got turned up and took after the trim tab with a mind of it's own. Honest...that's my story and I'm sticking to it.