The button hook is a small (approx. 10 cm) iron hook - often with a (decorated) iron, wooden, bone or ivory handle - with which the ladies' boots used to be tied (1). There is also a model with two hooks of different sizes. Another model is foldable.
Sometimes the button hook is fitted with a shoehorn at the other end.
See also pocket knife. [MOT]
(1) The button hook was sometimes used as a hook for eviscerating poultry (PETITPRERE: 2131). See further the folding hunting knife.
EMMET: 187 states that the button hook was used for gloves.