The 1/2 rail is a restraint if it prevents physical freedom of any kind. Most equipment cannot be labeled as always a restraint or always not a restraint.
RAI Manual pg P-1 says, "DEFINITIONS PHYSICAL RESTRAINTS Any manual method or physical mechanical device, material equipment attached adjacent to the resident’s body that individual cannot remove easily, which restricts freedom of movement normal access one’s (State Operations Manual, Appendix PP)."
It is not simply what piece of equipment it is but how it is used. An alarm can be considered a restraint if, every time a resident gets out of a chair and the alarm goes off, the resident is placed back into the chair. That example came from a state survey manager. Just yesterday, a surveyor explained that there are no objective rules for what is a restraint and what isn't; it depends on the resident, the device, and the situation. Use best judgement, erring on the conservative side. MDS culture should be resident-focused. What is best for the resident, not what is easiest for the staff (almost direct quote from the state survey manager).