[steamloco76]

I just received a box of Nikon stuff including a very clean Nikkor 105mm f/1.8 manual focus AIS lens. The focus ring will not move at all. Nothing looks bent or out of round. Aperture is clean and snappy. Glass is nice too. Any ideas on why it is stuck tight?

[BigMackCam]

It's probably dried out lubrication in the focusing helicoid. Not uncommon with old lenses, and the effects can range from a gritty or stiff action to complete seizure. Ironically, the better, finer-machined helicoids with very tight spacing are often more prone to seizure. You'll need to either service it yourself, or have someone do it for you...