LotR -- Book 1 - Chapter 12 - Flight to the Ford

[Hookbill the Goomba]

However, I don't think Wraiths are in one place or another: They have no visible form, but are able to affect the real world.

The Nazgul are product of what I call "Saurons Perfect Necromancy (SPN)".
I like to think of it like this;
The Barrow Wights were essays in the craft, just like the lesser rings were to the Smiths of Eregion.
The Nazgul were perfection in the craft, Like the Tree Elven rings.
Do you see where I am coming from?

Back on topic;
Glorfindel tells Strider to keep the hilt of the Morgul blade, so that Elrond can read the runes from it. To me this seemed very similar to the happenings in the Hobbit concerning Glamdring and Orcrist.

Also, I found that here, the Black riders seem to embed their greatest fears in Frodo. Although, to me, they seemed more threatening when they were an unknown shadow in the shire. At least back in the shire Frodo ran but with not as much fear as he had now. He now knows what they are and where they are from, this seems to leave him even more afraid of the, with obvious reasons.

Fear now filled Frodo's mind. He thought no longer of his sword.

At Weather-top Frodo actually considered fighting, but now he is certain that he cannot match up to them, and with no hope falls into disperse.

I think it is here that the desire for the ring works against Sauron. If it was not so precious to Frodo, his will may have broken there and he would have given up the ring with no second thought. However, his great desire for the ring helps him to hold out ageist them.