How do you make a gui pop up when a tool is equipped?

For a game, I need a gui to pop up when a tool is selected, so the player can click on the gui to build something. How do I do it?

Use the Equipped event: http://wiki.roblox.com/index.php?title=API:Class/Tool

Then when the tool is equipped in the equipped function move the gui to the playergui from somewhere in your game like inside the tool itself.