Seven Ways you can become a knight

1-Knight By Birth

The simplest way to become a knight is simply to be born one, by being a legitimate son of a noble family and not being too physically ill or mentally unstable to cope with the duties of knighthood. Many of the more exclusive orders of knighthood only admit such “ born knights “ due to snobbery.

2-Knighted in an Emergency 

In a true emergency like when a besieged city does not have enough knights to properly man the walls, members of the middle classes can be hurriedly knighted and given swords and armour to prevent the city from falling to its foes. Although they are often turned down if they try and join the more exclusive knightly orders and although they are often not permitted to pass their knighthood status down to their children, they are still knights with all the rights and privileges and the duties of knighthood. 

3-Killed a Knight and impersonated him

If you are a bandit and you happen to come across a lone knight, and you are able to overpower him and kill him, then if you dare to do so, you can steal his horse, armour, shield and weapons and impersonate him to gain the multiple privileges of knighthood.
But if you are uncovered as a false knight and taken alive, then you can expect a public execution, probably preceded by torture, for not just committing a murder, but also bringing disgrace to the knight’s knightly order or house and striking a blow at the class system itself.

4-Brought Knighthood with money 

If you happen to come from a really wealthy but non noble family that made their money in trade or some other “ non- noble “ way, then in most countries you can de facto “ buy” a knighthood by paying a large enough bribe to the King or equivalent ruler. In some countries this may be outright illegal, and/ or the ruler takes the money and still refuses a knighthood for you, and if you do become a knight you may face snobbery from your fellow knights who do not see you as truly one of them.

5-Knighted on the Battlefield 

An ordinary soldier who does something truly heroic, like saving the life of his King in a pitched battle can be knighted there and then on the battlefield, the medieval equivalent of a battlefield commission in modern times. As he is not born to knighthood some of the more exclusive knightly orders may reject him, and he might or might not have the right to hand his knighthood down to his sons.

6-Promoted

In the Roman legions, the third in command was a professional soldier who had earned the rank of the highest centurion of the legion and with it came a knighthood and a promotion to the equestrian class. In theory at least an ordinary legionary could start at the very bottom of the rank ladder and climb it over many years to reach this rank, the highest rank that a non noble legionary could possibly hope to reach. Your world might have a similar path to a knighthood.

7-Demoted Baron

Very rarely, a knighthood could be a punishment and a disgrace rather than a promotion and an honour. If a Baron disgraces himself in a way that is not quite serious enough to result in his execution or a sentence of life imprisonment, he could be “demoted “ and become a knight, still noble but shorn of his castle, his fiefdom and his exulted noble rank.