Reel Foot
From The Angler's Dictionary — your encyclopedia of fishing rods, reels, and tackle
The reel foot is the flat, tapered extension at the base of a fishing reel that slides into the reel seat on the rod. It locks the reel to the rod and must fit securely to prevent wobble during casting and fighting fish. Reel feet are typically machined from aluminum or formed from graphite, depending on the reel's construction.
Reel feet come in a standard width that fits most reel seats, but slight variations between manufacturers can occasionally cause fit issues. A reel foot that is too wide will not slide into a narrow reel seat, while one that is too narrow may wobble even when the reel seat is fully tightened. High-end reel seats (like Fuji or custom-turned seats) are designed for broad compatibility.
On spinning reels, the reel foot extends downward from the body so the reel hangs beneath the rod. On baitcasting reels, the foot extends upward so the reel sits on top. This difference in mounting orientation is one reason you cannot use a spinning reel on a casting rod or vice versa — the guide alignment and reel seat design are specific to each type. If a reel foot becomes bent from a drop or impact, it can usually be carefully bent back to shape, though severe bends may compromise the metal's integrity.