This crossing was straight forward.
Iran (Time to process: one hour)
Pass the entry gate into the customs border compound. There is a hut immediately on the left in which your vehicle details are noted.
Drive down the road to the right, and go to the building by the fence on the left hand side of the road. Present your Carnet in this building. Your vehicle chassis number will be checked, and the Carnet completed.
Back in your vehicle, and drive to the mini roundabout. Take the LEFT fork - do NOT go to the border post yet. Along this road, there is a building on the left with a large car park in front. Call in there to have your details entered into a computer.
Back down to the mini roundabout. This time, take the left fork towards the border.
Pull up at the first barrier, and go into the office on the left. More details are entered into a giant ledger here. Then move your vehicle into the compound beyond the first barrier. Here, they process your exit visa.
Finally, you go through the border post and into Pakistan.
Pakistan (Time to process: half an hour)
After going through the border post, park in the compound to the left at the end of the road. Go into the office which is at the end of the border post road. Here your visa is processed by three people in sequence.
Then drive about 1km to the vehicle inspection / Carnet compound. I was escorted by a pickup to this compound: it would not have been possible to find the place otherwise.
Following the Carnet completion (with only the chassis plate being checked), all formalities are complete.
There are no charges on either side of the border.