If a person used a safety pin or a number of safety pins before Shabbos on a garment to attached 2 garments or to mend a garment for TEMPORARY purposes to keep things together, can it be carried outside without an ARUV?
The safety pins that are needed to keep the garment together etc. even though they are temporary are needed for the garment now and are considered a part of the garment, and may be carried outside on Shabbos. However any extra pins that are not needed to keep the garment together should not be worn outside. This is the same as when women put bobby pins in their hair or sheitel, even though they are only temporary it is permitted.
Shulchan Aruch O:CH 303-8,17.