source has a trapezoidal cross section and the holding element 20 has a corresponding trapezoidal cross section that is somewhat larger than the cross section of the light source in an alternative embodiment the holding elements 20 for holding the light source are not designed as containers but as bolts onto which a light source with a corresponding recess can be plugged as shown in fig6 a plurality of support structures 19 and a plurality of holding elements 20 fastened thereon for holding the light source 16 can be arranged on a model 10 the number and position of the holding elements 20 is governed by the number and position of the required installation points and alignment points fig7 shows a flowchart of a method for installing an elevator in an elevator shaft in a first step s 1 the model is arranged in the elevator shaft in a second step s 2 the shaft dimensions are checked during this check of the shaft dimensions it can for example be checked whether a nominal depth of the elevator and a nominal width of the elevator as illustrated in fig1 are available over the entire height of the elevator shaft if the checking of the shaft dimensions turns out negative the model must be rearranged in the elevator shaft if appropriate there is also a need for a further step s 3 to adapt the shaft for example by removing material from a shaft wall if by contrast the checking of the shaft dimensions turns out to be positive two options are available in step s 4 in the first option.