lane spaces
 

How far can a player back up from marked lane spaces when the ball is in the shooters hand. Did a search, and I believe it is 3 feet, but can't find it in the rulebook. Also, does their entire body have to be within that area or do they just have to break the plane of the 3 ft boundary to be considered in a marked lane space?

3 feet.

Make them stand within the space.

NFHS rules 1-5-2 and 9-1-9.

The answer is zero inches. :D

The player may back up from the FT lane line, but he may not back up from the marked lane space, which is 3 feet deep. That would consitute leaving a marked lane space.

Also breaking the plane of any boundary of the lane space with either foot is illegal, but it is okay to have other body parts break those boundary planes prior to the ball striking the ring or backboard.

The reference for this would be 9.1.9A Sit c - I'll post it since I looked it up! :)
...couldn't remember how explicitly this was covered in the rules - legal without contact.