A whisker pole is a removable spar on a sailboat used to push the clew of a headsail (jib or genoa) out to windward when sailing downwind, typically in a "wing-on-wing" configuration. It allows the headsail to stay filled and stable by preventing it from collapsing behind the mainsail, increasing downwind performance, stability, and speed.

Key Aspects of Whisker Poles:
Function: It keeps the headsail projected out of the mainsail's wind shadow, enabling efficient, steady sailing on broad reaches or dead downwind (100° to 180° apparent wind).

Components: The pole connects to the mast (inboard) and the headsail clew (outboard), often supported by a topping lift (up-haul) and a foreguy (down-haul).

Types:
Fixed Length: A single-length pole designed for a specific sail size.

Telescoping: Adjustable-length poles, such as those from Forespar, which can be retracted for storage and adjusted to fit different headsails.

Usage: Commonly used in short-handed cruising and non-spinnaker racing to avoid the complexity of a spinnaker.

Difference from Spinnaker Pole: While a spinnaker pole is used for spinnakers, a whisker pole is specifically designed for headsails only.

Using a whisker pole significantly reduces sail flopping and improves control in varied wind conditions, making it an essential tool for efficient downwind cruising.