Methods for producing slots in tube walls are described and illustrated, along with devices for producing slots in tube walls. In some cases, a first number of punches arranged in a row pierce through the tube wall and in so doing produce slots, followed by another number of punches piercing through the tube wall in such a way that the slots produced by the first number of punches alternate with respect to the slots produced by the second number of punches. Also, in some cases an internal support is used, whereby small slots are first produced in the tube wall while the internal support is within the tube. After the internal support is removed, the slots are widened to finished dimensions. The internal support can include upper and lower parts designed to engage one another in a sawtooth or undulating manner.