> ## 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.

# Power supply install

> Mount the power supply unit onto the right rail of the frame.

## Installing the power supply

Next you mount the **power supply unit (PSU)** - the large silver box that converts wall power into the 24 V your printer runs on. It bolts to the back of the right-side rail.

<iframe src="https://iframe.mediadelivery.net/embed/697805/44cc98e1-61d2-40cf-a6c3-80fda710804e?autoplay=false&preload=false" style={{ width: "100%", aspectRatio: "16/9", border: "none" }} allow="encrypted-media; picture-in-picture" allowFullScreen />

<Info>
  For this step you need the **two M4x20 screws** (silver, blocky heads) and the **number 4 Allen wrench** (second largest).
</Info>

<Frame caption="Step 2: mounting the power supply to the right rail">
  <img src="https://mintcdn.com/intellectualpoint/O5GrjWnEycOQFaAQ/images/intro3d/assembly-step-2.png?fit=max&auto=format&n=O5GrjWnEycOQFaAQ&q=85&s=8c69b6ab805304cf340f12c947d6a652" alt="Diagram showing the power supply being mounted to the right side rail" width="1930" height="1084" data-path="images/intro3d/assembly-step-2.png" />
</Frame>

## Step-by-step

<Steps>
  <Step title="Find the two screw holes">
    On the back of the PSU (the side with the "power supply" sticker) there are two screw holes about six to eight inches apart. These line up with the two holes on the same track of the **right rail**.
  </Step>

  <Step title="Orient the PSU">
    Set the PSU on the right side of the printer with the **power switch and cable facing outward** (to the right) and the sticker facing the rail. Slide it toward the back.
  </Step>

  <Step title="Insert the screws through the rail">
    Push both **M4x20** screws through the rail holes so they poke out the back. Raise the PSU about an inch to line up its holes with the screws.
  </Step>

  <Step title="Thread and tighten">
    Hand-thread each screw into the back of the PSU, then tighten fully with the number 4 Allen wrench until the heads sit flush in the rail and the PSU does not move.
  </Step>
</Steps>

<Check>
  The power supply is bolted to the right rail with no wiggle, the power switch and cable face outward on the right, and both M4x20 screw heads sit flush in the rail.
</Check>

<Warning>
  Do not plug anything in yet. We connect power near the end of the build, after checking the voltage selector switch.
</Warning>

## Up next

With the power supply mounted, next you install the **LCD control panel** on the front-right rail.