Sprint is LeftShift, Shift Lock is LeftCTRL
Those two come straight from the official Roblox description, which has listed them unchanged through the Update 5.5 and UPD 9 eras. They are the whole movement kit you need for the mail-route loop: hold LeftShift to sprint between houses, and toggle LeftCTRL for Shift Lock so the camera stays over your shoulder while you thread gates and corners.
Two further actions are documented in the game's earlier, longer public description — preserved on Medal's game page — which labeled Q as Dash and E as Hurdle/Vault for clearing obstacles mid-chase. That wording is no longer in the current description, so this page keeps the “community-labeled” badge on both rather than presenting them as creator-current.