Taking apart a measuring tape is a simple project for those who want to clean the inside and lubricate the parts, or for someone who is simply curious to know what's inside. Work on a clean surface so as not to introduce more foreign material into the body of the tape measure, unless you intend to take it apart and not put it back together.
Use the screwdriver to remove the screws on the casing of the tape measure. Begin by only removing the screws found on the perimeter, and leave any that are in the middle.
Remove one side of the casing. You might need to remove the center screw for this, depending on the model of your tape measure, but the center screw may also be holding the tape spool, so do not remove it unless strictly necessary.
Use the lubricant and the toothbrush to clean out any dirt and grime you can see.
Spray lubricant onto the tape spool.
Remove the tape spool with the screwdriver only if you do not care much about using the tape measure in the future for its intended purpose. Keeping the tension on the tape upon reinstalling the spool can be tricky. However, tape measures are fairly easily replaceable if you decide to try this.
Replace the case and screws if you wish to put the tape measure back together.