Apple Macintosh PowerBook 190 Series - Manual (Page 162)

12 Gently touch the metal surface on the right side of the inside of the computer to
discharge any static electric built up on your body.
This protects your RAM card and PowerBook from damage.
Don’t walk around while you’re installing the card. If you do, make sure you
touch the metal surface again before continuing.
Avoid touching the heat sink inside the computer
(shown in color here). If the computer has been
on for a while, or the power adapter has been
plugged in and charging the battery, the heat
sink may have become hot. You may wish
to allow it to cool for a few minutes
before proceeding with the
RAM card installation
procedure.
Touch the inside of the computer in this area to dissipate
any static electricity that may have built up on your body.
157 Installing a RAM Expansion Card