Cutting Bottles to Make Glasses
The rig is made of scrap 2x4 and screws. The cutter is the Red Devil – just the cheapest well-reviewed one on Amazon.
The cutting process is well described elsewhere (for wine bottles mostly though what I had was beer bottles), so I will only add a few points:
Scoring continuously all the way around so it meets up with itself is essential. Without that (so, without a rig) you're pretty well guaranteed the crack won't follow the score.
Even after some practice, a majority of bottles had some deviation from the score. I've read beer bottles are more finicky than wine bottles.
The crack usually extends when applying cold water after hot (though not always); and you can see, if not always hear, as it moves.
Separating the halves usually requires a gentle pull, but occasionally just falls apart.