This paper describes the functions and variation in the use of PALM-UP in bidirectional French - LSFB (French Belgian Sign Language) interpreting. Data from final-year students of the Master's degree in Sign Language Interpreting at UCLouvain (Belgium) were analysed. Results show that PALM-UP is polyfunctional in both datasets of interpreted productions. PALM-UP was used as co-speech gesture and in signing by all participants, but some variation is observed across individuals. One of the most frequent functions in the dataset is planning (i.e., PALM-UP is used as a filler while preparing upcoming discourse or while making a cognitive effort in editing a term). PALM-UP was articulated while preparing upcoming discourse in LSFB target productions, whereas it was also used for this purpose and in combination with repairs, repetitions, word lengthening and pause fillers (i.e., while a cognitive effort was being made) in French target productions. When interpreting from French into LSFB, PALM-UP was sometimes articulated in the interpreter's non-dominant hand while the dominant hand was articulating one-handed signs. This phenomenon allows interpreters to keep the non-dominant hand active and to have shorter transitions between one- and two-handed signs in order to save time in their renditions.