The Schluter®- DITRA-TROWEL, KERDI-TROWEL, and DITRA-HEAT/-DITRA-XL-TROWEL feature square-notched designs to effectively install DITRA, KERDI, DITRA-XL, DITRA-HEAT, and DITRA-HEAT-DUO, respectively.
 
KERDI-TROWEL features a 1/8" x 1/8" (3 mm x 3 mm) square notch