The frequency versus length‐to‐thickness ratios for the thickness/shear and thickness/twist modes inBT‐cut quartz plates are given. TheC44thickness/shear frequency is calculated and this mode is identified in contoured circularBTplate by x‐ray‐diffraction topography. The electrode‐length to plate‐thickness ratios for suppressing the anharmonic overtones in bothATandBTplates as a function of electrode thickness are derived and compared with those measured on partially electroded quartz plates. The use ofBTplates as singly resonant and coupled‐mode resonators is discussed.