how do i remove the carriage on my brother KH 840 carriage is jammed?

Hi Victoria,
Take the yarn out of the yarn feeder and remove the sinker plate assembly. If the yarn has wound itself round the brushes remove it. Then remove the yarn that has tangled in the needle hooks. Once this is done it may be possible to move the carriage across the knitting in the same direction as you were knitting. You will lose the knitting! Then you should be able to slide the carriage off the end of the bed to inspect it.
Hoping this will help,

Sue
March 2010