Research related to the teaching and learning of the lunar phases reveals a low level of understanding of this astronomical phenomenon by most students of all educational levels. Therefore, there is a need to develop didactic materials to promote adequate comprehension of this phenomenon and which have been tried out in the classroom. Presented here is the implementation process of a didactic proposal for the teaching of the lunar phases at the primary school level, designed from a topocentric frame of reference. It includes the construction of an explanatory model of the phenomenon, based on observation of the Moon's motion in the sky. Its usefulness lies in that it does not require students to "place themselves in outer space" to describe the lunar movement and in its direct relationship with what they can observe with the naked eye every day. The proposal includes two diagrams that provide alternative images that support the construction of the model. The results obtained indicate that the proposal is effective in improving primary pupils' comprehension of the moon phases.