Fencing is a combat skill used to calculate chance to hit with piercing weapons.
Gideon's Advice: For training of weapon skills, it is best to have two characters fight each other, bandage each other, and use Anatomy on each other. Use a dagger for fastest speed and lowest damage. GMing Fencing, Tactics, Anatomy, Healing, and Parrying takes little time on UOR doing this. I would recommend gathering a lot of wool and/or cotton and making it into cloth before doing this to save money.
This might be a faster method:
Equip another character with high AR armor and put a weapon in their hands that they have 0 skill with. Hit them until you get to 81.0 shown skill, then equip them with a weapon they are GM with and continue to get the last 19 points. Having high dexterity significantly speeds up this process.