What tool do you use to connect your expression to an effect?

The pick whip is the tool used in Adobe After Effects to connect an expression to a specific property or effect within the timeline. It functions as a visual tool that allows users to create links between properties easily by clicking and dragging from one property to another. This is particularly useful for automating animations and creating dependencies between different elements in a composition.

When you drag the pick whip to another property, After Effects automatically generates the appropriate expression, establishing a direct relationship between the two properties. This not only streamlines the process of writing expressions but also helps users visualize the connections they are making within their projects.

In contrast, the other tools mentioned serve different purposes. The pen tool is primarily used for drawing and defining shapes or masks, the selection tool is for selecting and moving layers, and the transform tool relates to adjusting the position, scale, rotation, and opacity of a layer. None of these tools are designed specifically for creating expressions or linking properties in the way that the pick whip is.