What's a reverse lead out in cycling?

What's a reverse lead out in cycling?
Sprinters during stage 21 of the Tour de France 2023

A reverse lead out is similar to a lead out but instead of pulling the lead sprinter to within a close margin of the line and then dropping off - the lead out rider instead stays behind the lead sprinter. By doing so it allows the lead out rider to at a certain point begin to soft pedal (aka slowing down), effectively shutting off access to the lead sprinter's slipstream for any potential other lead sprinter from another team.

Diagram of a reverse lead out in action

This is similar to how teammates of riders in the break, may disrupt work in the peloton by being in front, but also not "working". It causes havoc in the organization of a work group for the peloton that is attempting to chase to catch the break up the road.

These mechanisms are all about removing the possibility of something rather than providing access to something. In a reverse lead out the lead out rider is removing access to the lead sprinters wheel which should provide a clear runway for the lead sprinter with no possibility another team's sprinter will dart out of their slipstream at the last second.

One could also argue that the lead sprinter is getting some drafting benefit given that we know drafting benefits occur not just from riding in front of an object, but also if an object is close behind. But that's not the main purpose.

This tactic is also colloquially known as "sweeping the wheel".

What is a lead out in cycling? | Pro Cycling Bets
We describe what a lead out is in professional cycling and how it can effectively be used by teams to win sprints.