Zor's Experiments Web Site 

Creating Skill Penalties By Joseph Larsen
In playing your character, have you ever tried to conceal your vehicles or gear outside of a city to avoid problems? How hard could it be to find your stuff? Have you ever just barely succeeded while making a fake ID? Was it just barely good enough? How difficult would it be to spot the fake? This optional rule goes hand in hand with the 98% skill optional rules found elsewhere on this site. It generates the penalties to others' skill rolls against your initial skill roll. If you succeed with an excellent roll, why not get credit for it? This rule is simply that:  If your natural skill roll is less than 10% of your skill percentage, then you set a 10% penalty to anyone that tries to undo your skill feat. (It is easiest to take the first number of the skill percentage rounded*)  If you roll under 5% (half of the 10%, rounded up) then you set a 15% penalty to undo your skill feat.  A natural roll of 01 ALWAYS creates a 20% penalty to undo your skill feat. Use common sense to determine which skills will use this. Demolitions would definitely be a skill to use this because someone might eventually diffuse the bomb, whereas fishing wouldn't use this rule. An example of this would be:
*HELP!: The easiest way to figure 10% without a calculator is to use the first number of the skill percentage and round to the nearest. For example 10 percent of 74% would be 7, and 10 percent of 75% would be 8. Why? Because if the second number is larger that 5, then go to the next highest number. Otherwise, leave it the same. Now, to find 5 percent, take half of the 10 percent. So 5 percent of 74% would be 4. (Half of 7 rounded up.) 