I am new to rod building. I bought a TFO 4pc rod blank and when you put the pieces together, they don't seat down all the way, leaving about 1/2" of the unfinished part showing. Do I sand down? Cut? Stuck at this point as I don't want to do the wrong thing. Any help appreciated.

Is it a spigot ferrule? If so, they do not seat all the way together.

The space is there to allow for future wear. Don't sand anything, use as is.

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Ok great, thank you

Kevin

No, do not cut, sand down or otherwise alter the ferrules.

From your limited description I suspect the ferrules are reinforced sleeve-over ferrules. Regardless of whether the ferrules are spigot or sleeve over, do not alter the ferrules.

For the female section of each ferrule I suggest you make a ferrule reinforcing wrap with a length equal to about twice the female ferrule's diameter. End the wrap as close to the end of the female ferrule as you can manage.

You could also make a reinforcing wrap immediately aft of each of the "unfinished parts", but do not extend the wraps onto the "unfinished" areas.

What you see as unfinished (and it does look odd at first) is an extension of the male portion of the ferrule made to allow for ferrule wear over time. All ferrules wear, it's the way of things. If you alter the blank or make a wrap to hide the "unfinished part" you defeat the ferrule wear allowance built into the blank.

Did I mention that you ought not alter the blank - no cutting or sanding ferrules?

My GUSA fly rods were built without finish on the male side of the ferrule leaving a gap almost a big as yours, have fished them that way 12+ years or so now with no ill effects.