This strainer is used to catch or filter out any stones found in your urine. Place the strainer under your urine stream. Save any stones or objects that you find in your urine. Place them in a plastic or glass container to show your caregiver. The stones vary in size - some can be very small, so make sure you check the strainer carefully. Your caregiver may send the stone to the lab. When the results are back, your caregiver may recommend medicines or diet changes.