A horizontal shaft impact crusher comprises a crusher housing having an inlet for material to be crushed, an outlet for material that has been crushed, an impeller being mounted on a horizontal shaft in the crusher housing and being operative for rotating around a horizontal axis, a curtain against which material accelerated by the impeller may be crushed, and an adjustment bar for adjusting the position of said curtain relative to the impeller. The crusher is further provided with a cross beam to which said adjustment bar is connected, said crossbeam being adjustable relative to the impeller, and a curtain position indicator device indicating the position of the cross beam relative to the impeller, thereby indicating the position of the curtain relative to the impeller.