The extra beams on the top of the cross signify the three primary forces: Father, Son, and Holy Spirit.
The slanted beam on the bottom is where the feet of Christ are nailed. The feet represent Yesod, the sexual path. The beam is slanted because the sexual forces are disbalanced in the initiate and need to be corrected, straightened.
For thirty years I sought God. But when I looked carefully I found that in reality God was the seeker and I the sought. -Bayazid al-Bastami