It is not about watches but a knitted gauge swatch to ensure, that your gauge is correct for a project that needs to follow a certain pattern. A lot of knitters, that I have met, never make swatches, but when experienced knitters swear to them - and designers that are thinking up new patterns make use of them a lot, I have decided, that it might just be a very good idea to do swatches. OK I admit - did not do it with the scarf pattern, but mabve.... just maybe it would not have cause me fear/headache to change to a new skein halfway.
I was working on a UFO (UnFinished Object) when I eyed a skein of yarn that might be perfect for a similar project, but the stitch gauge for 10x10 cm are completely different albeit it feels like they have the same thickness:
Black yarn (the UFO):
HOSUBAND from ISTEX - 80% wool 20% nylon
16 stitches - 24 rows on needles size 4
Red/greyish yarn: TOTEM from KAFIA - 100 % acrylic
12 stitches - 16 rows on needles size 6
The pattern are designed for the HOSUBAND yarn, so what if I used the same number of stitches and needle size for the TOTEM yarn? And if I was to use the suggested needle size for TOTEM I would have to calculate some changes to the pattern. I know that you should go up or down a needle size if your knitting gauge is more tight/loose as the pattern's required gauge - but these are two different types of yarn?
It worked - above swatch met the required knitting gauge. Now I just need to finish the UFO before I start the red version.