Gary --

One's for the "up button" action, the other for "down button". That's because the lack actuators are small DC motors, and to reverse them you must reverse the polarity when applying power.

Incidentally, the motors have a small thermistor (to prevent burn out when you drive with your arm out the window, holding the button down for 10 miles). The thermistor is about the size of a nickel and squeezed between two spring clips. It has a silver coating on each face which can tarnish, causing intermittent motor action.

Also, when reassembling the motor, if the tiny plastic "rack gear" is installed flipped over (it'll go either way) that motor will operate backwards from the others. I've done that more than once!