The function of the form is to act as a throttle stop when the part is in the position shown in the picture. It prevents full movement of the throttle when canopy is not securely closed and sealed.
When the canopy is closed, the latch is moved by pushing the bottom part of the latch towards the outside of the plane. This moves the throttle stop out of way and actuates the canopy seal.
See this Youtube video for an example, latch operated at 0:25.