White door stop
Door stoppers or holders: functions, types, installation : White Door Stop
Quote from Article entitled Door stoppers or holders: functions, types, installation:
Portable door stoppers could be either set in or taken away when it is necessary. The most common form of the portable door stopper is a wedge with a non-slip base, which is placed under the door leaf, keeping it open. There are also stoppers which have non-slip legs and should be placed on the lower door end.
The full version of the article can be found here.