Excellent! A new paper proposes a framework for talking about tDCS montages!

Figure 1. Subgroups of tDCS montages: (A) unilateral monopolar, (B) unilateral bipolar, (C) unilateral multiple monopolar, (D) bilateral bipolar-balanced, (E) bilateral bipolar-non balanced, (F) bilateral multiple monopolar, (G) midline monopolar, (H) midline bipolar-balanced, (I) midline bipolar-non balanced, (J) dual channel- bipolar, (K) dual channel midline double monopolar, (L) dual channel bilateral double monopolar.