Other Italian harpsichords employed plectra of leather. The guzheng is plucked by the fingers with or without plectra. "Plectrum" has both a Latin-based plural, "plectra" and a native English plural, "plectrums". Modern harpsichords frequently employ plectra made with plastic, specifically the plastic known as acetal. The plectra used are made from special ivory so that plucking can be done easily. Plectra for psalteries and lutes can be cut similarly to writing pens. In harpsichords, the plectra are attached to the jack mechanism. The plectra of a harpsichord must be cut precisely, in a process called "voicing". Musicians have used plectra to play stringed instruments for thousands of years.