This is a custom spanner made for holding the fuel pump assembly in place while the retaining ring is loosened or tightened. Allowing the pump assembly to spin could result in damage (kinked hoses or damaged float typically), and precise indexing of the assembly is needed to ensure the float/fuel level sending unit works properly. This spanner makes it easy and doesn't damage the plastic assembly.

Works well simply printed in PLA 6 Wall loops 25% gyroid infill