Immediately after sounding, pass the biopsy device to the same depth as the sound. Once inside the endometrial canal, withdraw the plunger on the sampling device, to produce suction within the device.
Quickly rotate the device between your thumb and index finger, while moving it in and out, within the endometrial canal. This in and out movement, with rotation, allows for fairly complete sampling of the surface of the endometrium.
Be careful not to withdraw the device far enough that the suction is lost. Once the sampling device completely fills or stops filling, remove it completely.