Put it outside the door, put on your shoes and walk out of the mat directly, indicating that it will be safe after going out. Red means good luck, good luck. Especially some people who go out to do business are particularly particular about it. Stepping on the red mat always makes me feel more comfortable. I believe this business will be smooth and profitable.
When I came back, I stepped on the red mat to keep all the bad luck out of the door, and all the lucky ones were brought in. Because red can also ward off evil spirits and keep all evil spirits out of the door.
But it will be more convenient to put the doormat inside the door, because you must put on slippers when you come back from the outside. If the doormat is inside, you can change shoes by stepping on the doormat and put it directly in the shoe cabinet, so as not to dirty the floor. Change your shoes on the insole when you go out.