The ornamental design for a channel, as shown and described.
FIG. 1 is an enlarged a front, top, and end view of a channel that has the design.
FIG. 2 is top plan view of the channel.
FIG. 3 is an end view of the channel.
FIG. 4 is a front elevation.
FIG. 5 is an opposite end view; and,
FIG. 6 is a bottom view. The back is also planar, and looks the same as the bottom.
The width of the channel may vary.
The channel is used as a post for fencing or screens, with the fence or screen elements fitting into the channel in the front. The channel can also be used as a rail or a picture frame.