Conceiving and/or using of scenarios, in online training design, are complex tasks. For designers and users, these tasks are performed from an “open instruction”. Cognitive artefacts can be included into instructions, in order to improve instruction comprehension and resource appropriation. Within Pairform@nce, a French national project that aims to develop ICT competency for in-service teachers, several cognitive artefacts are joined with the instruction. They seek to facilitate comprehension and appropriation of scenarios, named “training paths”. The current paper presents a (a priori and a posteriori) study on the role that artefacts play in task comprehension and in path appropriation.