The wedge is mounted between the tripod and mount, or tracking unit. This allows the mount to be aligned equatorially so that the tracking axis is then parallel to the Earth's axis.
This polar wedge was specially developed for iOptron Mount SkyGuider Pro. The polar wedge included with the SkyGuider Pro is perfectly suitable for wide-angle images. However, if you want to take images of Deep Sky objects using a telephoto lens or a small telescope which require longer exposure times, this equatorial wedge by William Optics is superior. It makes fine-tuning the polar height and precision orientation easier. However, this polar wedge is larger and heavier. So it would not be wrong to have two wedges... The supplied, lighter one for wide-angle images and the heavier version by William Optics for longer exposure times.