Since we have been discussing basic considerations in order to determine whether a slip-form is feasible, we should include the elevator requirement in arriving at a conclusion. One advantage of slip-forming. as mentioned before, is that the elevators can be started before the building is lopped out. This is especially true where the portion of the building containing the elevator shafts and equipment rooms is a stable structure within itself and can he slipped In the top and completed very early in the job. On tall buildings where the shafts cannot he .slipped to the top ahead of the balance of the building, it is possible to get a head start with the elevator installation by establishing a rail line based on the first seven or eight flours and projecting it upward in similar increments as the shafts are completed. It is also necessary to block off the shaft at some point below the slip-form to protect the elevator constructors. The most important thing lo consider is the alignment of the shafts for, once the rail line for the first segment is established, it is necessary to continue this line for segments above, This makes the elevator-front design more important than ever.