To be more specific as a Theater Technical Director:
It is basically my job to be in charge of anything not handled by the artistic staff. When a show begins production, we usually have a meeting with the:
Scenic designer: which is sometimes me for simpler shows, but usually a professional scenic artist who has read the script and come up with a set design that is full of awesomeness.
Director: who is in charge of the rehearsal and production process (usually an outside person from the community)
Costume designer: who is in-house and is responsible for designing, procuring, and fabricating costumes (and ours is AMAZING.)
Artistic and/or Executive director: who is in-house and ensures that the artistic direction of the production will go in a direction that is suitable for the community and its audience, as well as fits the theme of the season he/she has curated. Executive director would also be in charge of setting budgets for each department
Technical Director: me, in house. I am responsible for identifying scenic, lighting, and safety engineering problems that may arise (like designers making pretty staircases without hand rails, or placing lighting instruments too close to flammable drapes, or saying "no, you may not cut a 4-foot hole in the floor and install a hydraulic stage lift.")
Choreographer: if applicable
Music director: if applicable
From there, we dive in and begin our work. My job from there is to procure materials and build the set within the budget parameters, coordinate transportation of the set (depending on if we're doing shows here or at the larger theater downtown). I often am responsible for finding and hiring lighting designers, painters, and master electricians (who do the bulk of the physical light hanging and focusing and wiring so the designer can just press buttons). I'm also responsible for finding back stage run crew if the director doesn't already have some in mind. This all leads up to "Tech Rehearsal" which is usually the weekend before opening. At that point, the actors have a rehearsal (without costumes usually) with the intent of putting the tech together with the art. Its often a grueling day of stops and starts as the crew is learning when things get moved on stage, the actors are "finding their light," and the entirety of everything gets put together for the first time. I like to use the analogy of making a key by hand with a file to fit a lock. Each tooth on the key is like each of the elements; lights, set, acting, music. Up until that Tech Rehearsal day, the only prep you can do to make the key fit is communication; a description of the tumblers in the lock. Its a day of trial and error and fine tuning where there is a lot of filing of brass to make things work, but once the key fits and turns the lock, its like a well-oiled machine. That day really belongs to the director and the tech director. We're the two people filing the bulk of the brass to make the key work.
Once tech rehearsal is over, my job usually has a few tweaks before opening night; a paint touch up here, a hinge adjustment there. Once the show opens, my only job is to fix something if it breaks. Its about that point where I'm meeting with the next team to plan the next show and I get busy again. The only other thing I have to do for the first show is strike the set when its over.
Of course, being a small community theater with only three of us in-house, it is also my job to clean bathrooms, get food and drinks for concessions, act as house manager, box office, and generally schmooze guests into opening up their wallets for donations.
Needless to say, I've had a lot of 100-hour weeks and the couch in my office is often my bed.