Fist automatic jammer can be handled with only one hand: first pull of the line opens the jammer– the line (sheet) will slack, second pull of the line makes the jammer block the line. The automatic jammer is operated with the line (sheet) only. The jammer can be operated from distance of the length of the line and is very convenient in use – allows continuous control of the trim of the sail without holding a tight sheet line. Just one pull to slack the line and another pull to hold it.