Image: Naughty Dog / PlayStationOfficial screenshot from Naughty Dog / PlayStation.
Sharpest Tool in the Shed is the silver trophy for collecting all five toolboxes, which raise Joel's tool level for workbench upgrades. They are found in Bill's Town, Pittsburgh, The Suburbs, The University and Bus Depot.
The first three have a second chance later in the same chapter. The University toolbox is behind the shiv door at the end of the science building's second-floor corridor, and the Bus Depot one is in a FEDRA triage tent. Miss them and you will need another playthrough to finish the set.