An impact device for an elevator installation includes an impact part and a free-fall mass. The impact part is arranged on a rail of the elevator installation such that the impact part is supported on a sliding bracket attached to the rail. The free-fall mass is guided so as to move relative to the impact part. The guiding of the free-fall mass is configured such that the free-fall mass, initially raised to a determined free-fall height, transmits to the sliding bracket, at the end of its free-fall path and via the impact part supported on the sliding bracket, an impulse which is dependent on the determined free-fall height. Further, the impact device can be used in a method for post-adjusting rail securing devices for an elevator installation.

The invention relates to an arrangement for auditing straightness of a car guide rail, the arrangement comprising: a car guide rail mounted in an elevator shaft; an elevator car connected to the car guide rail via a guide member, said guide member, in a straightness auditing mode being adapted so that the horizontal distance between the elevator car and the car guide rail to be audited is constant; a plumb line stabilized in the elevator shaft adjacent to the car guide rail; an indicator detachably attached to the elevator car, in vicinity of the plumb line; at least one visual recording device detachably attached to the elevator car, facing the plumb line and the indicator, for recording a displacement of the indicator relative to the plumb line; and a memory for storing recorded relative displacement. The invention also relates to a method for auditing straightness of a car guide rail.