MM
If you land wheel up on tarmac in a glass glider, you qualify for the white line award.
Many years ago a friend of mine completed his first ever 300 km for his gold C, with the wheel down (Std Jantar). Unfortunately he raised it to land on the grass.
Next day I almost did the same thing, in the same aircraft, when returning from a long X-country flight, the noise decreased when I was extending the gear. Fortunately the reduction in noise alerted me in time so as to not make the same mistake.