Marking apparatus is provided for carrying out the marking of programmed character strings upon brittle surfaces such as glass. The lines forming the characters are generated by a gas entrained stream of abrasive particles which are expressed from the opening of a nozzle located in close adjacency with the surface being marked. Switching of this abrasive particle string between marking and non-marking orientations is carried out by a diversionary flow of gas under pressure which is expressed into the stream at a rate effective to integrate with the abrasive particle and divert the marking stream away from a marking axis. A suction port is provided which removes particles subsequent to marking or having been diverted to a collection location. In one embodiment, the nozzle from which the marking particulate stream is expressed is maneuvered between lifted or retracted positions and marking positions in close adjacency with the surface being marked. As the nozzle is retracted, the particle stream issuing therefrom is diverted by the diversionary stream flow. To improve the switching action, a ledge is provided opposite the diversionary gas source. This ledge receives diverted particles for disposition through the noted suction port.