Abstract: A binding apparatus, for attaching loose sheets to a folder or file provided with a binding agent, comprises a hotplate (2) against which the folder is inserted through an opening (4) defined between supporting means (5, 6). The hotplate is kept constantly heated, while a time circuit controlled by means of a push button unit (10) activates an alarm means (12) when a set time is at an end. The regulatable time circuit is always zeroed when the folder is taken out of the opening, since the folder affects a light beam across this opening to a photocell which is connected to the time circuit (FIG. 1).