The mechanical skill allows a Sim to repair broken appliances, electronics, sinks, tubs, toilets, and showers at a faster speed which may eliminate the need for a repairman. Having some degree of mechanical skill also reduces the risk of a Sim being electrocuted when changing light bulbs, however, having the maximum skill level (10/10) does not eliminate the risk of getting electrocuted. Mechanical skill is also important in the promotion of the Sim's career, including (but not limited to), business, military, science, and law enforcement. In Makin' Magic, a Sim's mechanical skill affects the number of charges charms they make will have, and how many MagiCoins they'll get for performing on the wooden stage in Magic Town.
To increase a Sim's mechanical skill, have them read mechanical books from the bookshelves. In Livin' Large, using the KraftMatic Woodworking Table to make gnomes will increase a Sim's Mechanical skill. Higher Mechanical skill lets a Sim make gnomes faster, and increases the price each gnome can be sold for. In Makin' Magic, a similar table, the Kraft-a-Gargoyle table is introduced, which also increases the mechanical skill. In Makin' Magic, Sims can also increase mechanical skill by using the Prick-Me-Not Spinning Wheel.
The Sims 2Edit
This skill is mainly useful for repairing things, but is also needed to advance in some careers and majors[TS2:U]. If Open for Business is installed, it helps in building the Robotics and Toy Making talent badges. A Sim's mechanical skill determines the chance of getting electrocuted when attempting to repair a broken electrical or electronic object. It can be studied from a book, or learned by repairing broken items or by using the TraumaTime "Incision Precision" Surgical Training Station. In console versions, mechanical skill may be gained from the "Jimmy three fingers" rocket bench.
If the The Sims 2: FreeTime is installed, studying the mechanical skill from a book will increase a Sim's enthusiasm for the Tinkering hobby. There is also a broken down car which builds Sims' mechanical skill while they repair it.