1. If you want to put up a billboard at the door, we usually call it a "water sign". This is very common in hotels and shopping malls, and is usually made of metal materials.
2. In addition to traditional metal water signs, there are also many billboards of different styles and materials to choose from. For example, a coffee shop may choose billboards made of wooden frames to give people a warm and natural feeling.
3. If you need a billboard that is easy to carry and set up, you can consider using roll-up banners or X-stands. This kind of advertising stand can usually be folded for easy portability, and the surface can be spray-painted with advertising content, which is very suitable for promotional needs that require frequent changes of location or activity.