Nearly all modern cross country gliders have retractable gear. Just one wheel, that's all.
I certainly did not ever expect to be one of those eligible for a white line award when I finally qualified to fly the club Pegasus at Booker. After all, I was an instructor! Knew it all.
And so when I had jumped in the Peg for a lunchtime jolly, and my students were waiting my return impatiently, my circuit was an example of perfection, my approach impeccable, my touchdown in front of the admiring students didn't seem that different....though when I stopped moving, the glider felt a bit strange....a bit lower than normal. Yep. Wheel up. Fortunately only a green grassy smear on the glider belly, no other damage, except to my pride.
SAFETY MESSAGE NOW! ALERT ALERT!
If you see a glider on approach, and the wheel is NOT down, do NOT RADIO AND TELL HIM! The startle effect may cause the pilot to raise the nose while raising the wheel, and has been known to trigger an accident. While a wheel up landing is usually only damaging to the glider if it happens on tarmac. Hence the white line award at the annual dinner.
After that incident, my own routine became Glider over 1,000', wheel up.
Glider under 1,000' wheel down. Works for me.