Hiza-guruma (膝車), the knee wheel.

Nage-waza (throwing techniques), Ashi-waza (foot and leg techniques), Gokyo 1st set (Dai-ikkyo).
Required for: 11th Mon (green belt, British Judo Association); 3rd Kyu (green belt, JudoScotland); 2nd Dan (black belt, British Judo Association); 3rd Dan (black belt, British Judo Association); 4th Dan (black belt, British Judo Association); 5th Dan (black belt, British Judo Association).

About
-----
Tori blocks uke's knee with the sole of the foot and wheels uke forward over it, using rotation of the hands rather than strength.

Step by step (standard right-handed form)
-----------------------------------------
1. From a right-handed grip, drift your partner's balance towards their right front corner, drawing them slightly onto their toes.
2. Step your right foot out to the side, roughly level with their right foot and a shoulder-width away, toes turned out, so your body faces across theirs.
3. Place the sole of your left foot lightly against the outside of their right knee, at the kneecap. The foot rests there as a block: do not kick or push.
4. Turn both hands as if turning a large wheel to your left: your left hand pulls their sleeve down past your hip, your right hand carries their lapel up and across.
5. Their body wheels over the blocked knee. Keep the wheel turning until they roll over and land on their back to your left, and keep the sleeve in your hand.

Key points
----------
1. Place the sole lightly on the side of uke's knee, do not kick
2. Break balance to uke's front corner before the block
3. Turn the steering-wheel action of the hands all the way through

Receiving it
------------
You feel your balance drawn to your front corner, then a light block arrives at your knee and your body keeps travelling over it. You wheel forwards and land on your back. Your right sleeve is held; tuck your chin, turn with the rotation rather than fighting it, and slap with your left arm as your back lands.

Reference pages elsewhere
-------------------------
Hiza-guruma on the IJF technique reference (International Judo Federation): https://judo.ijf.org/techniques/Hiza-guruma

From Waza Book: https://wazabook.com/techniques/hiza-guruma/