Remove the cap from a water-based marker pen. Use a jumbo pen the first time you do this to make it easier to see and manipulate the parts of the marker.
Use the sharp edge of the cap, or the box cutter to remove the nib from the body of the marker. Force the material nib out of the top of the marker.
Remove any ink or paint inside the body of the marker and wash it out. Let the body dry completely.
Wash out the body and top of the marker with soap and water. These parts will be reused.
Cut a piece of the chalkboard eraser that is just slightly wider than the nib holder on the top of the marker. Use scissors to trim the new nib into the shape you want it; it can have a hard, slanted tip or a thick, flat tip.
Fill the bottom of the nib with a water based putty, which will hold the nib in place. Allow the putty about two to three hours to dry completely.
Drop a steel nut or a small marble into the body to help stir the ink when you shake it. Fill the marker body up with ink.
Replace the nib onto the top of the marker.
Seal the connection between the nib and the body of the marker with a thin piece of putty and allow two to three hours for it to dry.
Shake the marker well and turn it upside down until the ink begins to seep into the nib. The marker is now ready to use.