A writing implement mechanism comprises includes a tubular first element (10) having a central axis and including first and second walls (12, 14) presenting that include respective first and second edges (16, 18) defining a guide (20) extending longitudinally in a direction that is inclined relative to the central axis between a first end and a second end. The mechanism further comprises includes a second element (26) adapted to slide along the first element (10) and including a nib (28) sliding in the guide (20). The second wall (14) is offset towards the central axis relative to the first wall (12) in a direction that is radial relative to said the central axis (Z).