An agricultural header, the agricultural header comprises: a frame; an arm pivotally coupled to the frame, wherein the arm is configured to rotate about a pivot axis relative to the frame, and the arm is configured to support a cutter bar assembly; and a locking mechanism configured to selectively block rotation of the arm about the pivot axis, wherein the locking mechanism comprises: a pin movably coupled to a first element of the agricultural header, wherein the pin is configured to move between a first pin position and a second pin position relative to the first element, wherein the first element comprises one of the arm and the frame; characterized in that the locking mechanism further comprises: a biasing assembly configured to selectively urge the pin toward the first pin position and toward the second pin position; and a mount coupled to a second element of the agricultural header, wherein the second element comprises the other of the arm and the frame; wherein the mount has an opening, the pin is disposed within the opening, the opening has a first portion and a second portion, the first portion is configured to receive the pin while the pin is in the first pin position, the second portion is configured to receive the pin while the pin is in the second pin position, the first portion is configured to block relative movement between the pin and the mount about the pivot axis to block rotation of the arm, and the second portion is configured to enable relative movement between the pin and the mount about the pivot axis to enable rotation of the arm. a frame; an arm pivotally coupled to the frame, wherein the arm is configured to rotate about a pivot axis relative to the frame, and the arm is configured to support a cutter bar assembly; and a locking mechanism configured to selectively block rotation of the arm about the pivot axis, wherein the locking mechanism comprises: a pin movably coupled to a first element of the agricultural header, wherein the pin is configured to move between a first pin position and a second pin position relative to the first element, wherein the first element comprises one of the arm and the frame; characterized in that the locking mechanism further comprises: a biasing assembly configured to selectively urge the pin toward the first pin position and toward the second pin position; and a mount coupled to a second element of the agricultural header, wherein the second element comprises the other of the arm and the frame; wherein the mount has an opening, the pin is disposed within the opening, the opening has a first portion and a second portion, the first portion is configured to receive the pin while the pin is in the first pin position, the second portion is configured to receive the pin while the pin is in the second pin position, the first portion is configured to block relative movement between the pin and the mount about the pivot axis to block rotation of the arm, and the second portion is configured to enable relative movement between the pin and the mount about the pivot axis to enable rotation of the arm. a pin movably coupled to a first element of the agricultural header, wherein the pin is configured to move between a first pin position and a second pin position relative to the first element, wherein the first element comprises one of the arm and the frame; characterized in that the locking mechanism further comprises: a biasing assembly configured to selectively urge the pin toward the first pin position and toward the second pin position; and a mount coupled to a second element of the agricultural header, wherein the second element comprises the other of the arm and the frame; wherein the mount has an opening, the pin is disposed within the opening, the opening has a first portion and a second portion, the first portion is configured to receive the pin while the pin is in the first pin position, the second portion is configured to receive the pin while the pin is in the second pin position, the first portion is configured to block relative movement between the pin and the mount about the pivot axis to block rotation of the arm, and the second portion is configured to enable relative movement between the pin and the mount about the pivot axis to enable rotation of the arm. a biasing assembly configured to selectively urge the pin toward the first pin position and toward the second pin position; and a mount coupled to a second element of the agricultural header, wherein the second element comprises the other of the arm and the frame; wherein the mount has an opening, the pin is disposed within the opening, the opening has a first portion and a second portion, the first portion is configured to receive the pin while the pin is in the first pin position, the second portion is configured to receive the pin while the pin is in the second pin position, the first portion is configured to block relative movement between the pin and the mount about the pivot axis to block rotation of the arm, and the second portion is configured to enable relative movement between the pin and the mount about the pivot axis to enable rotation of the arm.