Standing desks have been made in many styles and variations. Standing desks may be specialized to suit particular tasks, such as certain variations of the telephone desk and desks for architectural drafting. Some standing desks may only be used while standing while others allow users to sit or stand by adjusting the desk height with an electric motor, hand crank, or counterbalance system.[4] Some desks are also constructed like teacher's lecterns, allowing them to be set on top of an existing desk for standing, or removed for sitting.