Who was allowed to go behind the veil in the tabernacle, and how often?
Only the high priest was permitted to enter behind the veil into the Holy of Holies, and he did so once a year. The veil separated the Holy of Holies from the main sanctuary and kept God's presence from the view of the priests during their daily ministrations.
Les explains that the veil in the tabernacle separated the Holy of Holies from the main sanctuary. The priests would practice their daily ministrations, but they would only come up to the veil; the veil kept God's presence from their view. Only the high priest, once a year, would come in behind the veil, which Les connects to the Day of Atonement. He also notes that the veil pictures the very body of Christ and was rent from the top to the bottom, signifying that no man had anything to do with it; it was an act of God.