What's the correct procedure here?

Turn off water at the meter, open all cold water valves, drain-close, then turn the main back on? The hammering is at a toilet in the main bath.

And somebody splain me how in the hay air gets in the line in the 1st place. No leaks per the lil arrow thingie on the water meter.

Hammer away, the warden is on my arse about it.

Does it do it with the washing machine or with all faucets? I relieved mine with hammer arresters at the hot and cold faucets on the washing machine. Quiet as a mouse now.

It only occurs when the terlet in the master bath is flushed (her's).

Sounds like the toilet valve (ballcock valve inside tank) is shutting off fast and causing the hammer shock. Turn down the water valve (cutoff) coming into the tank and slow down the tank filling up. Ballcock will turn off easier without the quick force that causes the hammer. If this doesn't work, you will need to add a water hammer arrestor at the cutoff valve under tank.

I thought this was going to be about something else.

If this is the cause, replace the fill valve in the terlet tank with the pedestal type. They shut off more gradually.

Thank you sir, that seemed to fix it. 4 flushes and no hammering yet.

You have to give your toilet mouth to mouth. Sucks to be you

Same here

Yeah, same here. I recall water pipes and getting hammered... but I digress.

Loose washer on stop some where