An agricultural header, comprising: a frame; a cutter bar assembly; an arm pivotally coupled to the frame, wherein the arm comprises a first end coupled to the cutter bar assembly and a second end, and the arm is configured to rotate about a pivot joint relative to the frame; and a locking mechanism (400, 600) configured to selectively block rotation of the arm about the pivot joint, characterized in that the locking mechanism (400, 600) comprises: a rod (402, 602) configured to extend laterally along the agricultural header, wherein the rod (402, 602) is configured to rotate in a first direction to transition the locking mechanism (400, 600) to a first position and rotate in a second direction, opposite the first direction, to transition the locking mechanism (400, 600) to a second position; and a hook (404, 604) coupled to the rod (402, 602) and configured to engage the second end of the arm, wherein the rod (402, 602) is configured to rotate in the first direction to engage the hook (404, 604) with the second end of the arm to block rotation of the arm, and the rod (402, 602) is configured to rotate in the second direction to disengage the hook (404, 604) from the second end of the arm to enable rotation of the arm. a frame; a cutter bar assembly; an arm pivotally coupled to the frame, wherein the arm comprises a first end coupled to the cutter bar assembly and a second end, and the arm is configured to rotate about a pivot joint relative to the frame; and a locking mechanism (400, 600) configured to selectively block rotation of the arm about the pivot joint, characterized in that the locking mechanism (400, 600) comprises: a rod (402, 602) configured to extend laterally along the agricultural header, wherein the rod (402, 602) is configured to rotate in a first direction to transition the locking mechanism (400, 600) to a first position and rotate in a second direction, opposite the first direction, to transition the locking mechanism (400, 600) to a second position; and a hook (404, 604) coupled to the rod (402, 602) and configured to engage the second end of the arm, wherein the rod (402, 602) is configured to rotate in the first direction to engage the hook (404, 604) with the second end of the arm to block rotation of the arm, and the rod (402, 602) is configured to rotate in the second direction to disengage the hook (404, 604) from the second end of the arm to enable rotation of the arm. a rod (402, 602) configured to extend laterally along the agricultural header, wherein the rod (402, 602) is configured to rotate in a first direction to transition the locking mechanism (400, 600) to a first position and rotate in a second direction, opposite the first direction, to transition the locking mechanism (400, 600) to a second position; and a hook (404, 604) coupled to the rod (402, 602) and configured to engage the second end of the arm, wherein the rod (402, 602) is configured to rotate in the first direction to engage the hook (404, 604) with the second end of the arm to block rotation of the arm, and the rod (402, 602) is configured to rotate in the second direction to disengage the hook (404, 604) from the second end of the arm to enable rotation of the arm.