All aviation instruments are precision instruments. While they are normally very reliable, it is important to check their functionality regularly and certainly check for obvious damage before each take-off. Pressure instruments must be airtight, otherwise they will cease to functionaccurately (or may not function at all). It is, therefore, unacceptable to fly launch with instruments with broken glasses. When getting into and out of a glider, make sure you pay due attention not to damage the instruments by kicking the instrument panel or allow the metal buckles on your parachute to swing around.