The invention relates to a masking system (1) for the masking of a crank chamber (2) of an internal combustion engine (3) during a surface treatment of a cylinder running surface (4, 41, 42) of a cylinder bore (5, 51, 52) of a cylinder (6, 61, 62) of the internal combustion engine (3). The masking system (1) includes a hollow masking body (7) with a connector segment (71) for the connection of the hollow masking body (7) to the cylinder bore (5, 51, 52) as well as a screen segment (72). In accordance with the invention, the hollow masking body (7) is configured such that the connector segment (71) of the hollow masking body (7) can be positioned on the cylinder bore (51) of the first cylinder (6, 61) at the crank chamber side during the surface treatment of a first cylinder (6, 61) of the internal combustion engine (3). The invention further relates to the use of a masking system (1) in accordance with the invention.