According to wikipedia, a normal squire daily job included:
- Carrying the knight's armour, shield, sword,
- Holding any prisoners the knight takes,
- Rescuing the knight should the knight be taken prisoner,
- Ensuring an honorable burial of the knight in the event of his death,
- Replacing the knight's sword if it were broken or dropped,
- Replacing the knight's horse or his own horse, if either be injured or killed,
- Dressing the knight in his armor,
- Carrying the knight's flag,
- Protecting the knight if needed,
- Taking care of the knight's horses,
- Accompanying the Knight to tournaments and during the time of war to the battlefield,
- Ensuring the armor and weapons of the knight were in good order
But I'm not sure how he could perform these job during a battle. My understanding is that in a battle, knights normally acted as the heavy cavalry, who were required to ride in formation, hold certain position and charge when necessary. Did the squires just trail behind? How could he manage stuff like carrying the knight's paraphernalia, replacing the knight's horse or weapons, protecting the knight etc. when there was a battle going on, the knight was in his own formation, and he was also supposed to protect himself?