Transitional weight is a concept that describes a common led syncopation. The basic idea is that a dancer takes the first two steps of a triple, but the third step remains unweighted—usually in a line or pose. Then, the dancer takes a weighted step on the & in order to get back on “normal” footwork.
Beginners are usually introduced to transitional weight in the hip catch. Take the basic hip catch pattern: from a leader’s right hand and follower’s left hand connection, the follower is wrapped up on the leader’s left side (roll in), and then the leader catches the follower’s hip on the roll out. The roll in finishes on count 4, and up to this point the footwork of both the leader and follower is normal.
On the roll out to the hip catch, the transition weight syncopation begins. For the follower, she unrolls as she steps down the slot on her left foot on 5. By the & of 5, she feels the leader’s hand on her hip and steps together or slightly down the track with her right foot in order to fill the hand. On 6, instead of finishing the triple with her left foot (which would take her away from the connection on her hip), she continues to fill the connection point of the hand on her hip and points the left leg in a second position line. The leader syncopates in the same way: stepping right, left on 5 & and then settling into the left leg and creating a line with the right on 6.
To exit, both partners need to take an extra step in order to make up for the unweighted pose on 6. This is the transition: the dancers transition their weight to the posed leg in order to fix their footwork. This transition usually happens on an & count before a downbeat so the footwork is fixed for the next two beat increment.
Continuing our example, the leader is going to give the follower a free spin exit from the hip catch. He shifts his weight to his right leg on the & before 7, which causes the follower to also shift her weight to her posed (left) leg. Now they are on their normal footwork: the follower can do a free spin on 7&8 just like the 3&4 of a normal free spin or inside roll while the leader does his triple on the side of the slot, then both anchor at the end of the slot on 9&10.
Transition weight is used frequently when a couple is creating extra stretch or holding a pose. Leaders need to be aware of when they are asking for transition weight in order to have the follower on the correct foot to initiate spins, and followers need to be comfortable with transition weight in order to maintain the connection during delayed movements.
To become more comfortable with transition weight, watch videos of pros dancing for examples of transition weight. Start by looking at various catches: hip catches, shoulder catches, etc. You may also see transition weight on slingshots, whips (especially two-handed whips), and when coming out of play.