Disclosed is a hoist mechanism comprising a lifting arm wherein: when the lifting arm is in a fully raised position, a projecting upper end section of a major part of the lifting arm extends substantially horizontally; an effective length of the projecting upper end section is made variable by the provision of an extension element adjustably fixed to it; and the lifting arm is variable in upstanding height by a provision of a lower end section slidably connected to the major part of the lifting arm, wherein both length and height variations are made by stepless adjustments.