Lowering operations (or removal of temporary propping) are usually required as part of the assembling process of large steel structures under construction, in order to release them from the temporary supports, which represents the final step of the erection phase. This paper is dedicated to the study of this delicate engineering operation, covering two distinct approaches for the solution of the problem and addressing both the design and the execution phases. Indeed, two simple numerical models are proposed herein for the required structural analyses, so as to allow the check of compliance of the structure with the safety requirements prescribed by applicable standards for this transient phase, both for the structure itself, as well as for the temporary supports (in most cases, steel towers are used for this purpose). Additionally, an itemized procedure, aiming the achievement of a safe operation at the construction site, is also outlined. Two examples of successful operations, for which the proposed techniques were applied, are finally presented.