blocking frame

[tskill]

Had a question on a block from the side and the frame of the man being blocked. Looking at the NF rules it looks like you would only be able to block them at the shoulder and below and no contact in the back. However I frequently see players block with either one hand on the front, one hand on the back when the other man is turned to his side. Is there any general accepted interpretation of the frame when the man is turned to his side? Do other refs call holding or an illegal block if the man is turned to his side and the man blocking puts a hand on the back or the front?