Watching for bricks as police bed down for long stay following Twelfth riots in Belfast
The lesson you learn on the Woodvale Road is to watch and listen. Watch for the next brick or bottle or petrol bomb, and listen to the officers stretched out along several hundred yards of that road.
On Friday and again on Saturday night there was evidence of planning for a long stay; for as long as is necessary.
You'll hear of 20-hour shifts, see officers grabbing any opportunity to rest on the pavements away from the frontline and see the meal packs being delivered.
The portable toilets are another indication that this policing operation is dug in – here to hold an important line.
And in the listening you hear the different accents – local officers and those others drafted in to help from across the UK.
Every now and again there is a tactical manoeuvre – getting the water cannon into a better position, deploying plastic bullets and live rounds.
The latter have not been used, but behind every riot there is the danger that police will be fired on or targeted with blast devices. So, it is about planning for every eventuality and the worst case scenarios.
On Friday and Saturday the police weren't playing cat and mouse with the rioters.
They weren't chasing them through streets or alleyways.
That is not the tactic of this part of the operation.
Rather it is to make sure this line only several hundred yards from Ardoyne is not breached.
So, it's about sealing any gaps with Land Rovers and officers and water cannon, with barking police dogs not far away.
On the Woodvale Road, the crowd numbers on Saturday were much smaller than on Friday, and the situation less tense.
And at Ardoyne there wasn't much of a crowd at all; suggesting confidence in this operation is growing and that no attempt will be made to push a parade through.
This had been a rumour on the Twelfth. No-one knows how long this operation will last.
They do know that with every day it is costing more – not just in money terms but in relationships that are being damaged.
Matt Baggott came to Northern Ireland to deliver personal/normal policing.
He needs the help of both communities to be able to do that.