I am having problems with changing my weedeater line on my Bolens weedeater... I have tried everything to take off the weedline case but it will not come off.. any suggestions?

Just above the head where the aluminim shaft enters the head there should be a small hole about the size of a nail. Put a nail into the hole and push on the nail as you rotate the head counterclockwise. The nail should drop into a slot and then the head will feel like its locked, just keep unscrewing.