The transom planking has been allowed to cure for several days until the extruded material became hard and rubbery.
The excess material is easily removed without any tools or special skills, all you need are your hands! Simply grab the blob of rubber and pull upward at a sharp angle, the material will pull off cleanly and leave almost no residue behind.
What you have left is a simple clean black line as wide as the slim jointed surface! No mess, no crazy clean up, just squish the planks together and let the excess ooze out and cure, then peel it off!