Locking device dedicated to mainsails. Specific section for the lock would require to be featured on the mainsail track. An insert fitted into the headboard car would fit into the reinforced locking section to activate the mechanism. Once locked, there is no longer any tension in the mainsail haylard. With no stretch in the halyard, the sail would keep its shape and powerness. Mainsail locking devices have been used on racing yachts for the past 15 years.