The use of sigils with hedge knights in battle.

[Ser Cregan Brook]

So, I have not been able to really find information on this topic.

The question I am pondering is: How do lords and kings determine whose side a hedge knight is on in the heat of battle?

It is made apparent in the Dunk & Egg stories that each knight has to have their own coat of arms (at least for their family if not for themselves) for tournaments. In the case of battle would hedge knights' continue to bear their own devices or would the lords hiring them pass out simple surcoats for identification?

If they bore their own devices does evrybody try to keep track of what sigils are on their side? This seems like a complicated process...

Or would everybody just assume the guy next to them was on their side and really hope the lines don't get too mixed up? Which, of course they would since battle is chaotic.

I've noticed in Dunk's flashbacks in the graphic novels Ser Arlan is wearing his own sigil in battle, should that be taken as common practice?

[Lion of the West]

Given that knights use sigil for identification and you want your lord to see just how awesome you are, I would say that hedge knights bear their own coat of arms into battle. Its no good for a knight if you fight heroically but because you look like everyone else you don't get credit for your actions. After all the books are crammed full of individual heroics so standing out and been seen in battle would be a strong thing in Westeros. Also at the cost of potentially being targeted by the enemy because of who you are.