As a full-time stairbuilder, I've learned that I can't always rely on premilled parts, especially when staircases get complicated. For example, I constantly use factory-made treads with pre-installed returns. This works great on a straight staircase with one open and one closed stringer: I just trim the closed end so that I get the correct overhang on the open side. But on a staircase with both sides open - which requires treads with returns on both ends - things get trickier. That's because the treads have to be ordered a couple of weeks before installation - before the exact measurement...

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