I had an anon query on tumblr awhile back on how sari pins were worn so I thought I would do a quick post on how brooches were worn in the 1930s and 1940s.
Pins and brooches were around earlier (e.g. 1900s/1910s) earlier and were like the Edwardian bar pin or a round, jewelled brooch. Generally they held the pleats at the shoulder together, around this time the pleats were often bunched and then fastened, the loose end could then be readily draped over the head if required as in the portrait of Sarojini Naidu.
But the prolific use of pins and brooches for sarees is in the 1930s and 1940s. In part this may be due to the fact that the 6 yard saree became very common and probably required some pinning for women unused to the style. The style also made it possible to display this kind of jewellery.
Apart from pinning the saree at the shoulder either by way of the elongated bar pin or an elaborate jewelled brooch (pics 1-4), the brooch was also used to pin the saree at the waist as in pics 5 and 6. While pinning on the left side seems an elegant way of anchoring the cross drape, you sometimes see brooches on the right side (pic 7) as well as anchored way up as in the artful drape of pic 8 (a similar drape in pic 5).
The brooches of pics 9 and 10 appear to be merely decorative given they are pinned to the blouse and the sari then draped so that they are displayed.
A modern version of the bar pin here.