The Math Toolbox offers targeted math training and support for the transition from school to university, aimed at first-year students in STEM programs (engineering, computer science, natural sciences, mathematics, and other math-related fields) as well as high school students in the study orientation phase. The focus is on the essential mathematical knowledge and skills that must be available in the early semesters to successfully follow non-mathematical courses. Motivated by concrete topics and tasks from the first year of study, areas of school mathematics are revisited, practiced, purposefully expanded, and any gaps are filled with an emphasis on skill acquisition and direct problem-solving. The modular concept facilitates a problem-oriented approach to learning.