COST
The estimated costs are based on current prices and may differ from costs given in the columns. And it's only an estimate. Costs can vary depending on the availability of materials or ingenuity of the experimenter.
$0-100 Less than $100
$100+ More than $100

DIFFICULTY
This is an estimate of the time, experience, and skill needed to build a project successfully.
1.) Easy. Beginner level; no special skills needed. Easy. No special skills needed. Anyone who can understand and carry out the instructions is old enough to do this project.
2.) Moderate. Beginner to Intermediate level. Moderate. A young person may need parental guidence.
3.) Moderate. Intermediate; some experience needed. Intermediate. Some experience required. Young experimenters will probably need parental help.
4.) Difficult. For the advanced amateur. Difficult. For advanced amateurs only. Young experimenters will definately need help.
5.) Very Difficult. Special skills needed, advanced amateur or professional only. Very difficult. Special skills needed. Advanced amateurs only.

DANGER
This is to alert you to the electrical, chemical, biological, or physical hazards associated with a project. It is only a general guideline. Although we've gone over the articles carefully, we can not guarentee that these assignments accurately reflect the real risks. The experimenter assumes FULL RESPONSIBILITY for their own safety. Neither Tinker's Guild nor Scientific American, Inc. shall be held liable in the event of injury or damages resulting from any projects featured on this CD-ROM (See Legal Disclaimer). PROCEED AT YOUR OWN RISK!

Danger: Level 1
No Hazards

 Safe. A responsible young person can do this project with minimal parental supervision.

Danger: Level 2 
Minor Injury possible

 Requires shop tools. Parental oversight advised.

Danger: Level 3 
Serious Injury Possible

 Use of power tools, chemicals or power supply presents a risk of serious injury. Parental oversight essential.

Danger: Level 4
POSSIBLY LETHAL!!

 THIS PROJECT COULD KILL YOU. USE EXTREME CAUTION. ADULTS ONLY!

UTILITY
These ratings provide my personal assessment of a project's usefulness for science fairs and home-based research. Shawn Carlson
Cool Project. A good contender for science fairs and home experiments.
This project is based on obsolete technology.
 Uses obsolete technology, but could be updated.
The project seeks to explore a problem that is now well-understod.
 Explores a problem that is now well-understood, but might still be fun or educational to do.
This column is of historical interest only.
Historical interest.