First of all, the type of sword that a knight used in battle greatly varied. There were the single handed arming swords, and the two handed longsword often called a hand and a half sword or a bastard sword, in order to differentiate it from the larger great sword. read more
When fighting against other armored knights, a man-at-arms would use a technique called half-swording, where he would grip the sword by the middle of the blade in order to thrust through the gaps of his opponent's armor. read more