The usual spelling is "salterelli" and they are the wooden pieces that hit the strings (plucking with quills called the plectra).

This may help you.

From the first reference, which is very good and may help you with other technical terms.

Harpsichord makers of today use either wooden or plastic jacks. The Jack consists of a body, tongue, spring, pivot pin, damper and plectra. Early harpsichords and spinets had jacks generally made of pear wood bodies and holly tongues. However accurately produced, the timber (kiln dried) will take in moisture, swelling in damp conditions and shrinking in dry conditions. This causes the jack to either stick or rattle in the slide, resulting in great frustration to the player.

I didn't find "jack mechanics" as a phrase, so I think you can use "mechanics with jacks".

From the second reference, which also has a sketch (scroll down the page -- the screen is completely blank and the text starts quite far down):
Jacks

On the distal end of each key stands a thin strip of wood called a jack. The jack contains the plucking mechanism and is the main unit of the harpsichord action. The height is usually about 5 — 8 inches, the width is about one half inch, and the thickness is about three sixteenths of an inch. Where the top of the jack projects above the strings, just below the jack rail, a small piece of felt is fixed to the side of each jack, and, projecting against the neighboring string, acts as a damper. A small, upright strip of wood that is about one inch in height, called a tongue, is inserted into a slot cut into the upper part of each jack. Projecting from the tongue at right angles is the plectrum, about one eighth of an inch in length. The plectrum is a small wedge of hard leather of bird quill. The plectra, now made of hard leather were originally made from the quills (flight feathers) of crow or raven. Quill produces a greater brilliance and clarity of tone than the leather plectrum. The tongue pivots on a pin that is inserted laterally through it so that the upper part can be pressed back and away from the string. It is normally kept upright by a small spring at the back. It is usually made of hog’s bristle.