When the Arrow button is selected, designers can drag Sprites out of their Inventory to the grid, as well as picking up and dropping sprites that have been placed.
The Wrench button allows designers to change the parameters of the Sprites they have placed. Each Sprite has an individual set of parameters that govern its behavior. These parameters include things like movement speed, damage, point value, etc.
The Eyedropper button allows designers to copy Sprites that are placed on the grid. This is especially useful when the designer has changed the parameters of the Sprite with the Wrench tool, because using the Eyedropper will create a clone of the Sprite with the changed parameters. This makes it easy to duplicate customized Sprites.
The X button allows designers to delete Sprites placed on the playfield. This action is permanent.