Passing in rugby league may only be in a backward or sideways direction. He was so bogged that he could move neither backward nor forward. The characters read the same backward as forward. Flight occurs either as hovering, or as forward or backward motion. The two indexing systems are convenient when describing skips as going backward or forward. A mirror typically reverses the forward/backward axis. The effects of backward masking is weaker than forward masking. The WordPerfect document format allows continuous extending of functionality without jeopardizing backward and forward compatibility. Hirschman introduces the concept of backward and forward linkages. Words such as "backward", "forward", or "square" can further indicate the angle. KEE had a complete rule engine with forward and backward chaining. The toes will prevent you from falling over backward. The F-mount has a significant degree of both backward and forward compatibility. That would seem like a terribly backward step to me. Russia was militarily weak, technologically backward and administratively incompetent.