Innovative possibilities of interacting with touch-based devices come with the cost of having interaction designers to determine if users consider the interactions natural and easy to use. It is safe to assume that user-centered design helps creating applications that better fit user requirements and one of its steps is prototyping. However, interaction designers sometimes skip the prototyping phase due to time or economic constraints or for a lack of proper tools. In order to help designers of touch-based applications this research presents an approach that allows designers to create their own application-specific hand, finger or tag-based gestures and evaluate these gestures using sketch-based prototypes for touch-based applications without requiring any textual programming. The development of a sketch based prototyping tool followed a user centered design approach with requirements provided by user experience designers from industry. The whole application suite was evaluated to determine its fitness for helping designers of touch-based applications. The evaluation process was conducted in three steps: first, a study with software developers determined the efficacy of the tool to create custom gestures for performing tasks in sketch based prototypes. A follow up evaluation investigated the performance of the tool as a prototyping tool for tangible applications. Finally this thesis reports two cases where this solution helped in the design of real touch-based applications.