The Lander Scale Screw is the one that holds the scale tight to the frame of the knife. There are four total on the knife-- two on each side. All four are the same T6 screw, part number P0050.
Why are these screws special? Oh you know... they perform the critical function of making sure your knife handle is secure and safe. Little screws. Big job. If you're reading this, it probably means you lost a screw somewhere, and you have firsthand knowledge of the sadness that can accompany a lost screw. We feel your pain.
We recommend adding a drop of Blue Threadlocker to the screws when reassembling your knife. This will prevent your screws from sneakily escaping into the abyss.
You're going to need a T6 scale screw to reassemble. We gotchoo'. Try this torx tool with Wiha bits. It's our favorite.