“The Door” is the name I like to use for a strategy I and many other controllers use at airports that can utilize only one runway. Here is a visual representation of what it looks like and an example of it in use, live.
At max capacity when the traffic is very high, it has eight legs. You don’t need to use all eight legs, they are just there as an option. As the traffic builds you’d add a leg, then another, then another, etc. The strategy keeps all aircraft within about 25nm of the airport at all times.
The most important part is uniformity. First thing I do when I open is measure 10nm from the end of the approach cone, with the drag and vector feature. Once I get the measurement, that’s where I’ll place leg four that parallels the final leg. Then I’ll measure out 10nm from the downwind legs for legs one and five. The downwind legs three and seven are placed 12nm away, on the edge of the third airspace ring at a class Bravo airport for example.
It’s important to have that uniformity because it helps you stay consistent and having everything even makes it easier to remember where things should be. Your goal should be that you have everything so uniform, you could walk away from your device for 30 seconds and know exactly where everything will be when you come back.
Second important thing is to make sure legs two and six turn so that legs three and seven are the same length. Draw a line between legs two and six, if it’s on an angle then you are not doing it right. You need to be able to have the option extend those legs if you need to make room for an emergency, spacing, a slower performance aircraft, etc. Without that uniformity then you run the risk of it becoming out of hand and loosing control over the airspace, stretching out spacing overall, taking aircraft further from final and the airport.
So I’m both constantly checking to see if, one, legs two and six turn at the same spot, and two, maintain 10nm spacing between the final leg and fourth leg.
It looks like it’s a lot of work, but it’s not once you get used to using it and it can greatly reduce your workload.