this is a trick I learned a while ago and it does essentially the same thing that nudging does but with a few extra steps. There's a simple way of doing it that can get parts to within 0.125, and a more complicated way that has en extra step and if you find a very thin fuselage block you can get parts as precise as the width of that block (I use a 0.05, because it's small enough for my needs and still easy to work with in-game). First you need to take a 0.5 length fuselage block and place it with the end on the outside of your plane near where you want your part to be. Then attach the part you want to nudge to the other side of the fuselage block and attach a cockpit to the part you are nudging. Now move the 0.5 length fuselage block to the opposite side of the part, and make a few more sections of it if you need to move the part pretty far. Now remove the cockpit (And if you want to do the more advanced method, put the cockpit on the 0.5 fuselage block and remove the part you want to nudge. Take your thin fuselage block and put it perpendicular to the 0.5 fuselage block, and add moltiple of these. Basically the 0.125 intervals that the nudged part can be moved in are offset by however thick the thin perpendicular fuselage block is. Now reattach the part you want to nudge and remove the cockpit again) now you need to extend the 0.5 length fuselage block and the part will move into the body of your aircraft. If you need to move it along a different axis, just attach more 0.5 length fuselage blocks to the one you just extended along whichever axis you need to move your part by. Now as long as the part is now inside a fuselage block (and regular blocks too I think, but I don't use them and I'm not sure how attach points work with them) you can rotate it four times to bring it back to where it originally was, and now it is attached to your plane. Then you just remove the other fuselage blocks you extended that are probably stuck in other parts of your plane now. It's confusing when you try and apply it to your own plane, but when in doubt just attach cockpits to everything and don't use the undo button and there's very little you can actually mess up. If anything is still confusing ask in the comments and I'll clear it up. Hopefully this helps!