  There are worldwide efforts to search for physics beyond the Standard Model
of particle physics. Precision experiments using ultracold neutrons (UCN)
require very high intensities of UCN. Efficient transport of UCN from the
production volume to the experiment is therefore of great importance. We have
developed a method using prestored UCN in order to quantify UCN transmission in
tubular guides. This method simulates the final installation at the Paul
Scherrer Institute's UCN source where neutrons are stored in an intermediate
storage vessel serving three experimental ports. This method allowed us to
qualify UCN guides for their intended use and compare their properties.
