Boarding

Boarding in ice hockey is a penalty called when an offending player pushes, trips or checks an opposing player violently into the boards (walls) of the hockey rink. The boarding call is quite often a major penalty due to the likelihood of injury sustained by the player who was boarded, and officials have the discretion to call a game misconduct or a match penalty (if they feel the offense was a deliberate attempt to injure) on the offending player. However, in the NHL, if the boarded player sustains a head or facial injury, the offending player receives an automatic game misconduct. If no injury is sustained, then a minor penalty will be called. In college ice hockey, the player does not need to be injured for it to be a major penalty. Boarding is usually assessed against a player when the opposing player is hit 4–5 feet away from the boards and hits one's head against the boards on the way down.
The usual rule of thumb is when a player "only sees the numbers" (i.e. the the opponents back) it is against the rules (as well as dangerous) to check this player. Many leagues and governing bodies allow some leeway with players sticking out their arms to obstruct the player in lieu of delivering a hard check as it is deemed safer. 
==References==
Category:Penalties