DOLORES (Device Optimized for the LOw RESolution) is a focal reducer instrument installed at the Nasmyth B focus of the TNG. The detector is a 2048 x 2048 E2V 4240 Thinned back-illuminated, deep-depleted, Astro-BB coated CCD with a pixel size of 13.5 µ. The scale is 0.252 arcsec/px which yields a field of view of about 8.6 x 8.6 arcmin. The instrument allows imaging through broad and narrow band filters as well as spectroscopic observations with resolving powers between RS=~500 and RS=~6000. A multi-slit mode, based on custom masks manufactured by a dedicate cutting machine, is also available. Please note that MOS programs are bound to strict constraints on the number of masks and on the time necessary to design and manufacture them. In particular, each program can request up to a maximum of 5 masks per night and 10 masks per observing run.