A cure for bipolar, depression, schizophrenia or other mental illness would be a state of recovery where no more symptoms were present and you were returned to health permanently. This is the one that is contentious in mental illness.
Typical king-size beds measure 78 inches wide, while queen mattresses are 60 inches, full beds are 54 inches and twin beds are 39 inches wide. Visit a lumber or home improvement store and request the wood to be cut the exact length to save you some time and trouble.
A standard twin mattress is 39 by 75 inches. A king is 76 by 80 inches. This means that a headboard for a king bed is going to be about 76 inches or wider, plenty wide enough to go along the length of a twin bed. Headboards are often slightly wider than the bed for which they are made.