In this chapter, we investigate graffiti removal as a crucial component of urban walls mundane governance. Drawing on an ethnography in Paris, we show that graffiti removal accomplishes a series of consecutive, sometimes simultaneous, ontological enactments that perform contrastive versions of urban walls. In official documents and during removal interventions, the 'same' wall can indeed be handled as the object of a specific kind of maintenance, as a quantified surface, as a controlled space of public expression, as part of an official decorum, and as an uncertain material composite. These versions offer a particularly interesting case of what Deleuze and Guattari call 'collective assemblages of enunciation', where the erasure of unofficial public inscriptions implies the practical articulation of the material properties of walls (stone, brick, paint, concrete…), graffiti (ink, paint…) and removal techniques (water, sponge, paint, sand, rags, chemical products…). Such ontological multiplicity is precious to better understand both the modes of existence of walls in the city and the politics of public order maintenance.