On December 15, 2018, about 0830 central standard time, a Cessna 120 airplane, N2496N, nosed over during a landing at the Beaumont Hotel Airport (07S), near Beaumont, Kansas. The private pilot and his passenger were uninjured. The airplane sustained substantial wing and empennage damage. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Day visual meteorological conditions prevailed in the area about the time of the accident, and the flight was not operated on a flight plan. The flight originated from a private airstrip near Emporia, Kansas, about 0800, and was destined for 07S.According to a statement from the pilot, the airplane began to pull right after touchdown on the dry turf runway. He applied a "lot" of left rudder to try and keep the airplane going straight. As the airplane continued to pull right, with full left rudder and full aft elevator, the pilot tried "tapping" the left brake. The empennage rose up, so he stopped using the left brake and just used the left rudder. The airplane nosed over as it approached the west edge of the runway markers. The pilot indicated that the right brake was locked during the landing. The brake was subsequently unlocked to facilitate moving the airplane from the runway. A Federal Aviation Administration (FAA) inspector examined the runway and reported that it exhibited surface witness marks consistent with a locked brake on turf. He also examined the airplane. However, the brakes were not locked when he conducted the examination and a reason for a locked brake could not be determined. The pilot, who is also an airplane mechanic, was asked if there were any anomalies found with the brake system after the accident. He indicated that he did not find anything definitive wrong with the brake system. He believed that something in the master cylinder caused the brake to lock. However, further inspection of the master cylinder did not reveal any anomalies. Additionally, the brake lines and wheel cylinder checked out "good" with no evidence of blockage, kinks, or bends. A review of FAA airworthiness documents showed that the brakes were modified from the original brakes to Cleveland Brakes on March 28, 1993 in accordance with Supplemental Type Certificate SA13GL.