The Combine heavily relies on imagery through logos, symbols, and propaganda posters to assure their influence on Earth and recall their presence to its residents. Combine units - humanoid and Synth - also bear insignias, logos and other markings. Many Combine posters are also scattered around City 17 and its sector (including the Coast, Nova Prospekt, etc.). Most of the time they include the two common Combine symbols (see below), with variants in color and image backgrounds. The Combine imagery is often quite abstract, and the intended messages can be very subtle.