Stephen, I am assuming that the refill is a Parker. If so, you will notice two tiny staking indentions at the top of the metal canister. They hold the black plastic cap in place. Hold the metal canister, and wriggle the black cap off. Calculate how much distance you need to retract the nib comfortably. Mark that amount on the top of the metal canister, and lightly grind or file that amount away. Deburr the ground area, and push the black cap back on. You won't really need the indentions again, because the spring and the mechanism won't let the cap come off again. The only downside I have ever found is that when you have to replace the refill, you will have to do this all over again.