A metering device for dispensing granular agricultural product from a bin, wherein said metering device comprises: a housing (40, 42) enclosing an interior space; at least one metering wheel (53, 54) for conveying agricultural product through said housing; and a gate assembly removably received within the interior space of said housing, wherein said gate assembly is configured to guide agricultural product through said housing, wherein said gate assembly comprises - a product gate comprising an arcuately-extending gate valve, wherein said product gate at least partially defines a channel within the interior space of said housing through which agricultural product can flow, a gate key configured to selectively secure said product gate within said housing, wherein rotation of said gate key is configured to cause a corresponding rotation of said product gate; and wherein said gate key is configured to rotate between an unlocked position and a locked position, wherein when in the unlocked position the gate key can be removed from said housing, and wherein when in the locked position the gate key is restricted from being removed from said housing, wherein said gate key is formed as an elongated cylinder with a longitudinal protrusion extending along an exterior surface of said gate key, wherein said housing includes an opening formed through a side panel of said housing, and wherein the side panel is formed with a notch positioned adjacent to the opening, wherein when in the locked position, the protrusion of said gate key is misaligned with the notch formed in the side panel, wherein when in the unlocked position, the protrusion of said gate key is aligned with the notch formed in the side panel. a housing (40, 42) enclosing an interior space; at least one metering wheel (53, 54) for conveying agricultural product through said housing; and a gate assembly removably received within the interior space of said housing, wherein said gate assembly is configured to guide agricultural product through said housing, wherein said gate assembly comprises - a product gate comprising an arcuately-extending gate valve, wherein said product gate at least partially defines a channel within the interior space of said housing through which agricultural product can flow, a gate key configured to selectively secure said product gate within said housing, wherein rotation of said gate key is configured to cause a corresponding rotation of said product gate; and wherein said gate key is configured to rotate between an unlocked position and a locked position, wherein when in the unlocked position the gate key can be removed from said housing, and wherein when in the locked position the gate key is restricted from being removed from said housing, wherein said gate key is formed as an elongated cylinder with a longitudinal protrusion extending along an exterior surface of said gate key, wherein said housing includes an opening formed through a side panel of said housing, and wherein the side panel is formed with a notch positioned adjacent to the opening, wherein when in the locked position, the protrusion of said gate key is misaligned with the notch formed in the side panel, wherein when in the unlocked position, the protrusion of said gate key is aligned with the notch formed in the side panel. a product gate comprising an arcuately-extending gate valve, wherein said product gate at least partially defines a channel within the interior space of said housing through which agricultural product can flow, a gate key configured to selectively secure said product gate within said housing, wherein rotation of said gate key is configured to cause a corresponding rotation of said product gate; and wherein said gate key is configured to rotate between an unlocked position and a locked position, wherein when in the unlocked position the gate key can be removed from said housing, and wherein when in the locked position the gate key is restricted from being removed from said housing, wherein said gate key is formed as an elongated cylinder with a longitudinal protrusion extending along an exterior surface of said gate key, wherein said housing includes an opening formed through a side panel of said housing, and wherein the side panel is formed with a notch positioned adjacent to the opening, wherein when in the locked position, the protrusion of said gate key is misaligned with the notch formed in the side panel, wherein when in the unlocked position, the protrusion of said gate key is aligned with the notch formed in the side panel.