Top photo shows the lever moved to the "set" position. This is the position that loads the trip device. Notice there isn't a safety tab on this side to keep the lever from popping out of the notch.
2nd pic shows the trigger. This is where the bow eye contacts that spring loaded plate and trips the pin.
3rd pic is a dumba$$ sticking his thumb on the trigger to show the engagement to you folks. When that baby locks, it makes a very loud >CLICK< noise and you can actually feel the boat lock onto the trailer, very awesome, like a space ship docking on a space station. Very secure feeling when this sucker latches the boat to the trailer and very easy to hear over the noise of the boat under power.