> ## Documentation Index
> Fetch the complete documentation index at: https://stem-docs.intellectualpoint.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Mount the extruder bar

> Lift the assembled extruder bar onto the gantry rails and thread it onto the lead screw.

## Putting the gantry together

Now you lift the whole assembled **extruder bar** onto the two upright rails. Three things must align: the rollers onto each rail, and the lead screw into the feeder's threaded hole.

<iframe src="https://iframe.mediadelivery.net/embed/697805/712ba4e5-b093-4797-870f-f3d3ac957e0a?autoplay=false&preload=false" style={{ width: "100%", aspectRatio: "16/9", border: "none" }} allow="encrypted-media; picture-in-picture" allowFullScreen />

<Frame caption="The assembled gantry, ready to move up and down">
  <img src="https://mintcdn.com/intellectualpoint/O9vEZP6xEEMFLHva/images/intro3d/ender3-anatomy.png?fit=max&auto=format&n=O9vEZP6xEEMFLHva&q=85&s=5dc65520bf7b876c07ccfbf3060e9a01" alt="Ender 3 with the extruder bar mounted on the gantry" width="1536" height="1024" data-path="images/intro3d/ender3-anatomy.png" />
</Frame>

## Step-by-step

<Steps>
  <Step title="Line up the rollers">
    Hold the bar level and set each pair of rollers into the V-slot of the left and right upright rails. It should rest on top of both rails.
  </Step>

  <Step title="Thread onto the lead screw">
    The lead screw needs to enter the **golden threaded hole** on top of the filament feeder. Gently push the bar down; when it stops, guide the screw into the hole and **turn the lead screw** by hand - the bar will thread down onto it.
  </Step>

  <Step title="Confirm the wire path">
    The cables and white PTFE tube must run up and over toward the **back**. If any wire is trapped under the bar, lift the bar off and reroute it.
  </Step>

  <Step title="Test the motion">
    Turn the lead screw by hand - the bar should rise and lower smoothly. Do not force it.
  </Step>
</Steps>

<Check>
  The extruder bar rides on both rails, threads onto the lead screw, moves up and down smoothly when you turn the screw, and all wires run to the back.
</Check>

<Tip>
  That lead screw is the whole Z axis in action - turning it raises the print head one layer at a time during a print. Seeing it work by hand makes the "layer by layer" idea concrete.
</Tip>

## Up next

Next you install the **belt** that drives the print head left and right.