For those of you who wonder what makes the flaps go up and down on small airplanes, here is a picture of the flap motor and transmission assembly. The electric motor provides the force and the transmission converts the spinning motion of the motor into horizontal movement which pushes the flaps either up or down.
Here is a picture of one of three bolts which connects the wing to the airplane. This one happens to be installed backwards which puts the tail of the bolt and the nut to close to control cables!
After turning the bolt around this is the end you should see, the head of the bolt.
But if the tail of a bolt is to long and gets in the way of things like the flap follow-up cable, you can take a grinder and cut it off.
But sometimes its the other kind of heads, the goofy ones, that you have to worry about the most!