M 6 x 60 Coach Bolts + Nuts. Bzp. Pack 50. (Also known as Carriage Bolts or Cup Square Hex Bolts). Low round head with square underneath to lock into wood. Used on Timber to Timber or Timber to Metal applications. The bolt is applied to hole in material & as the nut is tightened it draws the square section of the shank into the hole/wood & locks it leaving a low domed head finish.