A movement pattern where the hips travel backward and the torso folds forward while the spine stays neutral and the knees bend only slightly.
It is the pattern behind deadlifts, Romanian deadlifts, kettlebell swings, good mornings and every safe way of picking something up. It is also the pattern most new clients cannot do, because they squat instead: knees forward, hips down, chest dropping.
The teaching tool that works fastest is a dowel along the spine touching the back of the head, the upper back and the tailbone. The client pushes the hips back until the torso is about 45 degrees over, keeping all three contact points. Two sets of 8 at the start of three sessions is usually enough for the pattern to stick.
Then load it. A kettlebell deadlift for 3 sets of 8, then a Romanian deadlift, then a barbell pull from the floor once the pattern holds at moderate weight.