Proscenium Stages:	Position Names: Positions which run the width of the stage and are upstage of the proscenium are usually called "electrics." If these are not pipes, but fully-accessible hanging positions with catwalks for the electricians to walk upon, they may be called "bridges". Positions which run the width of the stage and are downstage of the proscenium arch are called "FOH" (for "front-of-house") positions. In some theatres, these are referred to as "coves" or "cats" (for "catwalks"), and in Europe, these, too, may be referred to as "bridges". Positions which run from DS to US (or, depending on your point of view, US to DS) and are upstage of the proscenium arch are called "tabs". Vertical pipes are, in general, called "booms". Booms which are downstage of the Proscenium are referred to as "box booms" (because they were, originally, located in the "opera boxes" on either side of the stage. In some theatres, these positions, too, are called, "coves". Another form of vertical position is the "Ladder" (two examples pictured). Many theatres have balconies with rails that can be used for hanging lighting fixtures; these are called, appropriately, "balcony rail" positions. In addition to pipes, bridges, and various catwalks, hanging positions can be triangular or square trusses; when these are vertical, they are called "columns". Position Numbers: Electrics, booms, box booms, and FOH positions are typically numbered from the proscenium out. For example, the downstage-most electric (the one closest to the proscenium) would be the "#1 Electric" (or "1E") and the electric just upstage or it (the second-closest to the proscenium) would be the "#2 Electric," etc. Likewise, the upstage-most FOH position (closest to the proscenium) would be the "#1 FOH" (or "FOH #1"), while the position just downstage of it would be the "#2 FOH", etc. Tab electrics are usually numbered from centerline out. On stage left, the tab closest to centerline is the "#1 Tab SL"; likewise, on stage right, the tab closest to centerline is the "#1 Tab SR". There are many variants of this system and you will usually find your show served best by your adapting whenever possible to whatever system is in place and already understood by the electricians who work in whichever theatre you're playing.
Arena and Thrust Stages:	The systems used to describe and number the hanging positions over arena and thrust stages vary even more than do those in proscenium theatres, largely because there is greater variety among them. This is an example of a typical arena or thrust grid: You will certainly find hanging positions which differ greatly from those described on this site, and frequently you will have to devise your own numbering and naming schemes. It is important that when you do so, you make your system clear and as easy as possible for the electricians to understand. Remember: if you really want to put a light in a specific place, even if there's no position there in the theater, you can generally find a way to do it - though that might turn out to be too expensive or time consuming. Don't design your lighting thinking, "OK there's a pipe so I'll put a light there"; think of what light you want to send to the stage, and from what angle, and if there isn't a ready-made position in that precise location, there's probably a way to rig one.