Lead
Lead is time that pulls a successor earlier so it overlaps its predecessor. It is written as a negative interval on a dependency, most typically FS-5d.
How to use it
"Start the security-audit paperwork five days before development completes" is written FS-5d. Work that would normally wait for the finish runs overlapped through the last five days. A negative interval can sit on any of the four relationship types, not only FS, though most leads met in practice are overlaps on FS. The compression technique called fast tracking is the organized use of exactly this overlap.
Why it matters
When the deadline is tight, lead is one of the few levers that genuinely shortens duration. It is not free, though: starting the successor before the predecessor is settled means redoing the successor if the predecessor's outcome differs from expectations. Lead trades schedule time for rework risk. This is why schedule-quality standards recommend avoiding leads altogether — a hidden negative interval is hard to see on the schedule, so even the fact that a risk is being carried gets forgotten. And as leads accumulate, the critical-path computation itself stands on overlap assumptions — the computed finish date drifts toward optimism.
Common misconceptions
Reading a lead-heavy schedule as a fast schedule is the misconception — it is a risky schedule. Before adding lead, consider splitting the predecessor instead: divide "development" into "core feature development" and "wrap-up," and the paperwork becomes an ordinary FS after the core part. The same overlap, but with an explicit statement of which part must finish first — more honest, and no conflict with quality checks. If an overlap does stay as a negative interval, each such link should carry a conscious decision that the rework risk is understood and accepted.
wbsgantt's predecessors support lead and lag intervals in working days, so overlaps are recorded as logic instead of pinned dates.