Chargers move at double their normal Move rate, but must make the usual deductions for crossing terrain and obstacles. For example, mounted Knights have Move 7 and so can charge up to 14" in the open. If moving through difficult terrain or over an obstacle, such as a wood or a fence respectively, they move at half their speed, reducing their charge distance to 7". If the obstacle is defended by enemy troops, the charging unit does not need to cross the obstacle, but only to reach it, and therefore it will receive no penalty to its charge move (see defending obstacles in the close combat phase).
A unit may charge across an obstacle, but the unit's charge distance will be halved (for example, a unit with Movement 8 that is placed behind an obstacle can cross it and charge an enemy up to 8" away on the other side of the obstacle).