My stepfather used to use the old tree spikes to climb trees into stands. He slipped one afternoon going up and one of the spikes caught in his leg deep in the inner thigh. He couldn't get himself off the spike, he hollered and hollered lucky one of the caretakers just happened to be clearing a trail not to far from him and heard him. He barely missed the femoral artery, but the doctor told him just by the blood already lost if that fella hadn't heard him he wouldn't have been long for this world. He never used a spike again needless to say, that was back in the late 80's.