🔍 It refers to where the guide **bearing** is mounted on the bit. A **top-bearing** flush trim has the bearing near the shank (at the top of the cutters), whereas a **bottom-bearing** bit has the bearing at the tip (bottom of the cutters). You choose one or the other based on where your template or reference surface is. If your template is on top of the workpiece, you’d use a top-bearing bit (the bearing rides on the template above the cutters). If your template or reference is underneath (like when using a router table or inverted situation), you’d use a bottom-bearing bit:contentReference[oaicite:48]{index=48}. Some projects even require flipping the work over, so you might use both types. There are also **double-bearing (top and bottom)** bits, which give you more flexibility – you can use them either way. But in summary: top-bearing for template-on-top routing, bottom-bearing for template-on-bottom or router table work.

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