Suggestion boxes have been used in factories to improve processes through a continuous improvement approach. From this perspective, the ideas with direct and quick implementation and visible results are favoured. This paper investigates the nature of design activities hidden behind the ideas suggested. The authors sort 132 ideas from a suggestion box of a French train maintenance center and highlight differences in the processing of the ideas through the suggestion box. The paper shows that a part of the ideas should have been rejected, as they present a gap in the design to be directly implemented. However, they are kept and collectively re-worked to be well adapted to the factory. This enriches literature on creativity and crowd sourcing for and by manufacturing. In particular, it gives a design perspective to innovation and continuous improvement in factory by revealing different design types in the box to fit the production system.