A platform unit for use with a scaffolding structure having a working deck, a substantially horizontal longitudinally extending first support member and a substantially horizontal longitudinally extending second support member, the platform unit comprising a worker's platform and a ladder for climbing onto the worker's platform, wherein the platform unit further comprises a first tipping prevention member (20, 50, 3) which is adapted to interact with the substantially horizontal longitudinally extending first support member of the scaffolding structure, and a second tipping prevention member which is adapted to interact with the substantially horizontal longitudinally extending second support member, which second support member is vertically spaced apart from the first support member characterised in that the second tipping prevention member is adapted to interact from below with the substantially horizontal longitudinally extending second support member, wherein at least a part of at least one of the first and second tipping prevention members (20, 50, 3, 30) is vertically adjustable for enabling attachment and detachment of the platform unit to said scaffolding structure, and in that the platform unit further comprises at least three rollers (5, 24, 28, 29, 36, 37) for supporting the platform unit, wherein at least three of said rollers are adapted to rest against the working deck and to transfer any vertical load acting on the worker's platform to the working deck when the platform unit is in a normal position, such that the platform unit is rollingly movable in a longitudinal direction, which corresponds to a direction extending along the length of the first and second support members (101, 102) wherein the platform unit is a free-standing unit, wherein the first and second tipping prevention members (20, 50, 3, 30) are arranged to guide the platform unit along the first and second support members (101, 102), and wherein the platform unit is configured for being repositioned laterally to the longitudinally extending first and second support members (101, 102) and then at least a part of at least one of the first and second tipping prevention members (20, 50, 3, 30) is configured for being vertically adjusted in order to attach the platform unit to the scaffolding structure. a first tipping prevention member (20, 50, 3) which is adapted to interact with the substantially horizontal longitudinally extending first support member of the scaffolding structure, and a second tipping prevention member which is adapted to interact with the substantially horizontal longitudinally extending second support member, which second support member is vertically spaced apart from the first support member characterised in that the second tipping prevention member is adapted to interact from below with the substantially horizontal longitudinally extending second support member, wherein at least a part of at least one of the first and second tipping prevention members (20, 50, 3, 30) is vertically adjustable for enabling attachment and detachment of the platform unit to said scaffolding structure, and in that the platform unit further comprises at least three rollers (5, 24, 28, 29, 36, 37) for supporting the platform unit, wherein at least three of said rollers are adapted to rest against the working deck and to transfer any vertical load acting on the worker's platform to the working deck when the platform unit is in a normal position, such that the platform unit is rollingly movable in a longitudinal direction, which corresponds to a direction extending along the length of the first and second support members (101, 102) wherein the platform unit is a free-standing unit, wherein the first and second tipping prevention members (20, 50, 3, 30) are arranged to guide the platform unit along the first and second support members (101, 102), and wherein the platform unit is configured for being repositioned laterally to the longitudinally extending first and second support members (101, 102) and then at least a part of at least one of the first and second tipping prevention members (20, 50, 3, 30) is configured for being vertically adjusted in order to attach the platform unit to the scaffolding structure.