A stage is assembled from modular decks, usually one by two metres, set on adjustable legs or a substructure. The decks are locked together into one stable surface, after which steps, handrails, a stage skirt and any floor finish are added. Because the system is modular, almost any shape can be built: a straight stage, a riser in a corner, a round island, or a stage on several levels. Assembly requires no drilling into the floor, so it can also be used in halls, churches and listed buildings.

Height follows from sightlines: for a small group in a flat room, twenty to forty centimetres is often enough, whereas a larger hall needs sixty to a hundred centimetres so people at the back can still see. Where there is raked seating or a sloping floor, the stage can stay lower. Size depends on what has to fit: a speaker with a lectern needs little space, but a panel, a band or a presentation with a screen quickly increases the depth required. Also allow for walkways at the sides, room for monitors and cabling, and a safe place to get on and off.

A catwalk is typically between one and a half and two metres wide, enough to walk and turn comfortably without looking narrow on camera. It is often set lower than a stage, so the audience on both sides has a good view and the distance does not become too great. An even, seamless and non-slip finish is essential, because high heels and gaps between decks are a genuine hazard. The structure also needs to be firmly braced, since walking creates a rhythmic load that is otherwise felt as vibration.

Stage decks have a stated load capacity per square metre, which must match the number of people and the weight of equipment, scenery and instruments. As height increases, steps with handrails and edge protection are required, and the rear of a stage is often screened or marked to prevent a fall in the dark. Working at height, suspended structures and trussing above an audience are subject to separate health and safety rules and an inspection of rigging points. A stage must also never block an escape route or emergency exit, which is taken into account when planning the room layout.

The most common finish is a molton skirt all round, hiding the substructure, legs and cabling. The surface itself can stay black, or be finished with carpet, dance vinyl or a colour matching the brand identity, which makes a considerable difference on camera. Lighting plays a major role: light along the edge or beneath the catwalk reveals its shape, while frontal light ensures faces are well lit. Where filming or streaming is involved, it is wise to match the finish accordingly, since glossy floors and bright edge lighting quickly become distracting on screen.