Centering helper for Black & Decker router

An aid to help positioning the router in exactly the right spot for drilling. After marking the correct position with a 90° cross of lines on the piece of wood, align the markers of the centering aid with the lines. This is possible at 45-degree intervals, so also works if the router needs to be angled to fit in the place where you need to drill.

Using this aide is much easier than trying to guess where the router bit or drill will end up when fully lowering it. For one thing, guessing correctly is made hard because drill bits like in the picture do not look symmetrical when viewed from an angle, as the groove of the drill is visible on one side but not the other. Furthermore, you typically need to re-position after turning on the router (it always "goes off to one side" a bit due to the sudden torque), and the spinning, blurry bit can be harder to see.

The design is customizable in FreeCAD. This one fits my Black & Decker KW850E. If you modify it to fit your router, please drop a line in the comments!

Why is the shape so weird?
To make it 3D-printable. A simple design would be to have very fine "needles" that need to align with the drawn lines, but these are too flimsy, also the minimum possible width of a 3D printed line is too thick already, as aligning the helper should work regardless of the direction you look from. So the approach here is to align with the edge of a 3D-printed area, and to always have 2 edges that align with the drawn line from either direction. Another aspect is that on small pieces, the drawn line sometimes ends already quite close to the cross, so this shape allows to align even in that case.