[3 On Da Tree]

Back where I grew up (Dakota's), That was called a cattle guard. In the summers I would help out on the Uncles dairy farms. Milking time was always 5:00 am and pm. The long days of summer the cattle couldn't tell time so us kids jumped in the pickemup trucks and headed down to the pasture to fetch the cows. Some were stubborn, so you gave them a nudge with the front bumper.
Hence the word's Cattle guard.