What describes devices that allow clients to stand while tanning?

Tanning booths are specifically designed to allow clients to stand while tanning. These booths typically feature multiple vertical tanning bulbs that provide an even tanning experience from all angles. Standing in a tanning booth helps to eliminate tanning lines and may make the session feel shorter for the client, as they can move around slightly while tanning.

The other options refer to devices that do not allow for standing. Sunbathing platforms generally refer to areas for outdoor tanning rather than a controlled environment like a booth. Horizontal tanning devices and lay-down beds specifically describe equipment where the client lies down during the tanning session, which is the opposite of standing. Thus, the defining characteristic of tanning booths is that they accommodate a standing position for clients, making them distinct in the tanning industry.