This special rigging system for this particular gear was developed to increase the horizontal fishing area of the trawl and comprises two identical trawls (“twin”) fixed together. The horizontal opening is provided by a single pair of otter boards, which are attached to the trawl close to the wings. Their inner wings are attached to a sledge towed simultaneously with the otter boards from a common crow foot. Another option used on modern vessels in the northern shrimp fishery is to tow the gear with three warps.
They are generally used for catching shrimp or bottom species.
Source: FAO site, 2017