Hooks and nuts work in conjunction with the flange and the tension band to apply and adjust tension to the banjo head. This particular banjo has what are known as flat hooks. This banjo is thought to be a 1930s era Slingerland. The Slingerland Musical Instrument Mfg. Co. was based in Chicago, Illinois and was owned and operated by H.H. Slingerland. The company changed names several times, including The Slingerland Banjo Company, Slingerland Banjo and Drum Company and others.