When working on the nosewheel steering and retrieving the sliders, I realized my small part F box would be empty except for one item. C75F4-6 was simply called "Gusset". Since I didn't recall seeing anything like that coming up, I figured I better see where this mystery gusset belonged. Sure enough, I found it belonged under the baggage floor and I somehow missed installing it when working in that area. Fortunately, I had left the baggage floor unriveted and the only rivets I needed to drill out were one longeron rivet each side. Turned out not to be a big deal to position, drill, prep, and rivet. Should have caught that when working the baggage area.