How does the Start No Later Than (SNLT) constraint affect my project schedule?
Project Central uses constraint type rules, along with work durations and dependencies, to determine the scheduled start and scheduled end dates of work items in your plan. With SNLT selected as the constraint type, the Scheduled Start date will be the earlier of the date entered or the start based on any dependencies. The Scheduled End date will be the later of calculated start + duration or the end based on any dependencies. This article describes how the SNLT constraint works.