The plançon à picot, or simply plançon (also spelled planson), is a medieval infantry

Infantry in the Middle Ages

Despite the rise of knightly cavalry in the 11th Century, infantry played an important role throughout the Middle Ages on both the battlefield and in sieges...

 weapon designed for smashing and thrusting. It consists of a stout iron-shod baseball-bat-like shaft (length 1-1.5 m) and a steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 spike attached on top. It was cheap and easy to make, and was extremely efficient on heavily armoured opponents, as it would be easily driven through armor. The weapon is a relative of the goedendag

Goedendag

The goedendag was a weapon originally used by the militias of Medieval Flanders in the 14th century. It was essentially a combination of a club with a spear. Its body was a wooden staff roughly five feet long with a diameter of roughly four inches...

, a popular weapon of Flemish militias of the 14th century. Given that the plançon à picot is recorded at several times as being carried alongside the goedendag, they may not be identical.