Poolristi küljes oli varjusihik, mida sai seada erinevatele kõrgustele, millega määrati mõõdetavate nurkade vahemik. Sihtimis- ja horisondisihik joondati visuaalselt horisondiga, ja kui varjusihiku heidetud vari langes horisondisihikule ja oli joondatud horisondiga, saigi nurga kindlaks määrata. Praktikas oli poolrist kvadrant täpne, kuid kohmakam kui Davise kvadrant.
The demi-cross supported a shadow vane that could be set to one of several heights. By setting the shadow vane height, the range of angles that could be measured was set. The transom could be slid along the staff and the angle read from one of the graduated scales on the staff. With the shadow vane's shadow cast on the horizon vane and aligned with the horizon, the angle was determined. In practice, the instrument was accurate but more unwieldy than the Davis quadrant.
