From the LIFE magazine article, Horse Roping in Nevada is a Picturesque Feat; 21 June 1937.
Photo 1 of 3 - Getting a Wild Horse ready for Hoof Trimming. The caption: "Four cowhands help Jack Case (right, rear) bring the struggling horse to its knees. Jerked off its legs by entangling ropes, the animal screams its dismay."