The rest of this paper is organized as follows: we will first explain the organization of the datatypes modelling the static behaviour of the graphical user interface. In Section 3, we will describe events and in particular how to generate them from user input. After this, we will embark on a guided tour through HTK's widgets (Sect. 4 to Sect. 9), covering basic widgets, menus, editors, canvasses, windows and tix widgets, finishing off with an overview of HTK's toolkit.