The phrase describes a layout, not a rule. Knowing how the two halves work helps you read a kennel's listing and judge whether a dog will be comfortable.
How the design works
Each run has two linked parts. The inside room is walled and climate-controlled. The outside part is open air with a concrete floor and a fence. A doggie door joins them, so the dog can step out for fresh air and sun or step in to rest on the bed. At Happy Paws, the 2022 kennel building has 50 indoor and 50 outdoor sections, with 25 doggie doors on each side, built with fire sprinklers and heating and cooling.
What is inside
Every run has a Kuranda raised bed and blankets, so a dog lies off the floor. Dogs see their neighbors through the fence but keep their own space. The kennel is described by its reviewers as immaculately clean, and the inside rooms are heated in winter and air-conditioned in summer. You can see all of this on a walk-through: tours run every day, 9 to 11 AM and 2 to 4 PM.
Where it appears in California law
California's pet boarding law treats an exercise run, a kennel or a room as a permanent or fixed enclosure, a structure that separates a pet from its waste. The law requires that such an enclosure let the pet turn around, stand, sit and lie down comfortably, and that it provide heating, cooling or shade as needed. An indoor/outdoor run meets the idea of choice by design: the dog picks the setting that suits the weather.
How it shows up in your booking
The word "run" is also the unit you book. The three classes are Economy, Business Class and First Class, with sizes from about 16 square feet inside plus 48 outside up to about 48 inside plus 72 outside. Read the kennel class entry for the rates, and are the runs heated and air-conditioned for the comfort details.
What to expect on a tour
Walk to the doggie door and look at both halves. Notice the sound level, the floor in the outdoor section, the bed and where water sits. Staff walk with you on every tour and will point out a run that fits your dog's size. A few visitors find it helpful to look at one run in each class, since the step from Economy to First Class is easy to see in person. Watch your step on wet concrete during cleaning.