If you do not need an actual, working elevator, you can create the illusion of one simply by using flat, sliding doors with small windows in them. These windows would be covered with translucent plastic or paper (allowing light to shine through, but still be opaque enough to hide whatever was behind them.

The illusion works as follows: On cue, two stagehands hidden from audience view pull open the doors. The doors slide open and your "passengers" enter the elevator car.   As the doors close, a light shines from within the elevator, lighting up the windows. Another stagehand (or the actor dressed as the elevator operator) simply (and slowly) raises a horizontal card that blocks the light for BOTH windows and gives the illusion of the elevator car "rising." This gives your passengers the opportunity to sneak out the back, hidden from audience view.

Then, when the elevator "returns," the operator merely lowers the card in the same fashion, revealing the lit windows once again. Doors open and -- voilia! -- either the elevator is now empty or it has been populated with a different set of passengers (who likewise have sneaked in the back way).

We used projections which made it look like the elevator was moving. The elevator was a free-standing piece and when Miss Dorothy and Millie got in to "tap" we lowered the lights on the surrounding set and the projection gave the illusion of movement. We were flying all of our other set pieces and didn't have the space needed for the elevator, plus it would have been too unstable. The high schools in our area did the show after we did and they flew the elevator. Unfortunately, it got stuck with Millie and Dorothy in it about 6 feet up. It is a great effect when it does fly, but it is not necessary, especially when the show grinds to a halt with two leads suspended in the air in a box.

Welcome Leonarp! I havent seen a rolling scenic cloth drop used for years in this way great idea. Very effective if an open exspanding grill are used as the Lift doors. i have done the moving scene cloths across stage, using a crown & staight rollers off stage. I assume it could be considered an Olio!