Ha, gotcha. It's neither.
This cool little thing is a 'pitot tube', and it's part of the system used to measure airspeed.
The two tubes are connected to the altimeter by flexible hoses that connect to the right side of the device. At rest (no forward motion) the pressure in each tube/hose is equal. But, once the airplane starts moving the pressure in the upper tube is greater than the lower tube. This is because the upper tube has a hole in the front of it, but the bottom tube has holes in the side of it. The difference in air pressure causes the altimeter to accurately indicate the airspeed.
Why go to all this trouble? The problem is called a 'stall', which is when the airspeed over the wing is slow enough it looses lift and the airplane falls from the sky, typically resulting in a crash if close to the ground. So as they say, "Ya don't wanna stall, cause you gonna fall".
The close ups below show the insect protection device. I suppose you could call it an IPD, but I never heard anyone use that acronym :-)
IPD shown in the flying position, the wind hits the upper flap and lifts the cover from the opening in the front of the tube.
IPD in the resting position. Gravity pulls the cover down.
Now, you might ask, "Why isn't there a similar device on the bottom tube? Because it has very small holes, so the bugs can't get inside.
Joe Miller bought this on the internet, and it will be refinished to look like new before attaching to the glider.
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