From the LIFE magazine article, Horse Roping in Nevada is a Picturesque Feat; 21 June 1937.
Photo 2 of 3 - Getting a Wild Horse ready for Hoof Trimming. The caption: "Heavily thrown, the Nevada Stock Farm's Palomino is having its head firmly held down by a cowboy and Jack Case's cowgirl wife, while its kicking hoofs are tied."