Anchor is a very important tool in ROBLOX Studio. It is used both in ROBLOX Studio and in usermade tools. Applying an Anchor to a brick will prevent the brick from being moved while the game is running until it is unanchored.
To anchor something, click the Anchor tool. Then click the brick you want to anchor. To unanchor, click it again. To do this with the Properties panel, check or uncheck "Anchor."
Note that anchored parts will not move, and anchoring tools will cause the player to act anchored until they unequip the tool.
Anchored bricks can be used as baseplates, or they can act as bricks that you don't want being blown up by players in your place.