Method for safely installing a rolling scaffolding consisting of ladder elements raised vertically and platforms arranged horizontally between the lines of ladder elements, characterized in that, from the ground or from two ladder elements of the scaffolding that are raised vertically and are connected transversely by diagonal holding bars, bearing a fixed scaffolding platform arranged at a certain height on said ladder elements, it comprises the following steps: - raising two ladder elements on the ground or on each of said two fixed ladder elements of a same storey, - installing, horizontally and at a suitable height on said two ladder elements, upper and lower lateral ledgers (ledgers and under-ledgers) with the aid of a pole or a diagonal bar provided with a suitable handling hook, the ledgers comprising at each of their ends at least one hook (17, 19) and at least one ledger comprising at at least one end a lock (17a, 19a) able to engage on a ladder rung, one of the end hooks being able to slide on the engagement rung during installation such that the ledger positioned by means of its hook on the engagement rung is able to slide on the rung so as to allow the ledger to move backward such that the other end hook can engage on an engagement rung of the other ladder element, - locking said hooks (17, 19) on their respective engagement rungs with the aid of said lock (17a, 19a), and - fixing the diagonal bars of the two ladder elements which have just been raised, securely therewith, so as to hold the ladder elements rigidly in position, - installing from the ground or the fixed lower platform, at a determined height and below the ledgers, a scaffolding platform on the ladder elements which have just been raised, elevating its end portion provided with oblong fixing hooks, engaging its oblong end hooks on a rung of a ladder element and elevating the other end portion of the platform to engage its hooks on a rung of the other ladder element, by means of the longitudinal movement of the oblong hooks, and thus arranging the platform in a stable horizontal position, - accessing the platform, which has just been installed, via a trapdoor of the platform at one of its end portions, and - installing, from the accessed platform, the toe boards of the platform, the operator being protected laterally and over the length of the platform by said installed ledgers. - raising two ladder elements on the ground or on each of said two fixed ladder elements of a same storey, - installing, horizontally and at a suitable height on said two ladder elements, upper and lower lateral ledgers (ledgers and under-ledgers) with the aid of a pole or a diagonal bar provided with a suitable handling hook, the ledgers comprising at each of their ends at least one hook (17, 19) and at least one ledger comprising at at least one end a lock (17a, 19a) able to engage on a ladder rung, one of the end hooks being able to slide on the engagement rung during installation such that the ledger positioned by means of its hook on the engagement rung is able to slide on the rung so as to allow the ledger to move backward such that the other end hook can engage on an engagement rung of the other ladder element, - locking said hooks (17, 19) on their respective engagement rungs with the aid of said lock (17a, 19a), and - fixing the diagonal bars of the two ladder elements which have just been raised, securely therewith, so as to hold the ladder elements rigidly in position, - installing from the ground or the fixed lower platform, at a determined height and below the ledgers, a scaffolding platform on the ladder elements which have just been raised, elevating its end portion provided with oblong fixing hooks, engaging its oblong end hooks on a rung of a ladder element and elevating the other end portion of the platform to engage its hooks on a rung of the other ladder element, by means of the longitudinal movement of the oblong hooks, and thus arranging the platform in a stable horizontal position, - accessing the platform, which has just been installed, via a trapdoor of the platform at one of its end portions, and - installing, from the accessed platform, the toe boards of the platform, the operator being protected laterally and over the length of the platform by said installed ledgers.