Stencil

a device made out of cardboard or plastic, for example, in which a shape is cut out. The stencil is placed on a surface and paint is applied on top. This way, the paint on the surface will have the same shape as the stencil. The shape can be repeated endlessly thanks to the stencil.

EXAMPLE:
Hommage à Rosa Luxemburg by Jean Paul Riopelle 
Roadsworth's street art
Banksy's graffiti