John 19:17 So they took Jesus, and he went out, bearing his own cross, to the place called The Place of a Skull, which in Aramaic is called Golgotha.
One visible difference between a pole and a cross is a pole is like a 1-D line. While a line, by definition, needs two points to become defined; good and evil defines the law pole. Law is one way; linear pole, based on the two points of good and evil. The two thieves were under law and may have been crucified on poles. Jesus did not break any Roman law; Pilot washed his hands and let the mob decide. Jesus died based on mob rule; irrationality. This was unique and showed respect.
The cross, on the other hand, is in 2-D space, with four elements, or two sets of two points; two lines or two poles like an (x,y) grid. One pole was the vertical or the y axis; law, with Jesus also having an x-axis. Jesus and the cross was more than just law, but also faith and fate.
The Christian sign of the cross, used while praying, starts at the mind eye; above and between the eyes; Father. The bottom of the y-pole is next, at the heart/solar plexus. This is the son. The Holy Spirit, which was to be left behind, was the new x-axis or x-pole, left to right shoulder. The cross symbolized an addendum to the classic spirit. The spirit of truth was more that just blind 1-D obedience to law. The Holy Spirit, as the spirit of truth, was more advanced thinking than blind obedience to law. Blind obedience makes you linear. Whereas truth gives more of a sense of meaning and reasoning; 2-D thought and cause and effect.
The late Psychologist Carl Jung had the theory that all humans have four psychological functions; intellect, emotion, intuition and sensory. These help orientate us to reality. We all have these four, but different people will use them in different orders. This different order accounts for the variety of types of adaptation.
In terms of the cross, intuition is the head, intellect is the right shoulder, sensory is the heart/foot; touches the earth, the emotion is the left shoulder. The 1-D pole or y-pole of law is intuition and sensory (or know by heart). What was added to make the x-pole or x-axis of the cross was emotion and intellect; spirit of truth.
If you were only intuitive and sensory you would sense and have an intuitive sense of what to do next, but without knowing why other than it feels right or wrong. In a sense, law of good and evil was sort of a replacement for instinct, structuring behavior, but without have to know any good explanation; blind obedience of law as formerly had been for instinct.
The Holy Spirit brought more of the brain to the table and allowed one to ask why, allowing more access to two additional functions. It was no longer; one size fits all, but more in terms of shades of gray, which takes more nuisance of feeling and thought.
The death of Jesus at the hand of the mob, was also symbolic of the end of the age of the gods. Human had controlled the fate of the Son of God and even had him killed. The gods had been the means to structure the mind but this approach blurred sensory reality. Law was way to find new footing, at a time when the whims of the gods, in reality; the blur, would appear more statistical and less structured as cause and effect. With the age of the Gods, sacrificed, the two extra functions of intellect and emotion added another dimension; x-axis to consciousness, on a larger scale. It was the update from BC to AD, played out in symbolism, spread out over time.