Seminal plugs are hard waxy plugs of seminal fluid and cellular debris that build up in the inverted hemipenes. They have a long, tapered shape, usually with a rounded cap at the end which is closest to the cloaca/vent. When the plugs start protruding from the groove in the hemipenes into the cloaca or the vent, the feces passes along the top of the plug, usually coating that end. Often, the first sign of retained plugs that a lizard keeper sees is what looks like a small clump of feces stuck in the vent. What is actually being seen, however, is the top of the feces-capped plug.
Normally, these plugs, which form usually during breeding season, are expelled naturally during defecation. They may or may not be noticeable when the keeper is cleaning up the urates and feces. When they are extruded by the lizard during defecation (or as an isolated act, as with the melted cheese-like exudate discussed above), they may be so small as to be unnoticed, or may be covered by the feces. If the plugs are not forced out, however, they continue to grow in the inverted hemipene, eventually causing some discomfort.
What does need intervention as soon as they are seen are retained seminal plugs.
Once they grow in length as high up as the vent, the tops of the plugs begin to trap feces when the lizard poops. In time, you will see two pieces of hard smooth poop in the lizard's vent. You can try to remove them yourself. First, soak the lizard in a warm bath. Then using gloved hands or a couple of layers of facial tissue, gently rock one of the plugs from side to side as you gently pull. The plug should pop out. A bit of the hemipene may evert a bit with the plug but the hemipene should retract back into the tail. Repeat with the second plug, if there is one.