Abstract: A support system is provided for supportably securing a vertically movable support structure having a boom attached thereto to a floor structure of a building. The support structure extends through an opening formed in the floor structure. The support system includes a set of support brackets pivotably mounted relative to vertical support members of the support structure. The support brackets are supportably engageable with a portion of the support structure and a first floor structure in a first supporting position. The support brackets are freely swingable and movably engageable with a second floor structure as the support structure is moved relative to the second floor structure enabling the support brackets to be supportably engageable with the portion of the support structure and the second floor structure in a second supporting position.