Banner tassels

Is there a set length on how long the tassels on a banner should be? And how do you tie them?

I’ve only ever seen them slipped through a bight at the top.
In terms of length, you want them long enough to allow the bearer to hold them when holding the banner on the ground, so that if it’s windy, they aren’t blowing around in people’s faces so a little longer than the diagonal of the banner from top corner to opposite bottom corner.

i would have thought that isn’t something we need to worry about. Purchase a banner from a reputable supplier and they’ll know what is correct (i note you don’t ask for the length of the pole or size of the standard - these are not typically options to consider)

There is no published ‘correct length’. That said, they often come supplied as ‘super-extra-unnecessary-long’ length. Probably because the same places supply the RBL who seem to like them “comedy long”.
I always advised my Sqns to shorten them to the same approximate length that RAF Sqn Standards have their tassels - About the same length from the top of the pike as the Banner extends down the pike - depth - the short edge.

… ie if you laid your Banner out on a table with the Banner flat out at 90 degrees from the pike, the tassels - laid down alongside the pike - should be about level with the bottom edge of the Banner.

Adjusting them is easy… Pick one end to shorten (you could do both, but that’s extra work - just shorten one end and then adjust the cord so they are level)… The tassel is slipped over the cord. Slide it up and you’ll see that the cord is just turned over on itself and whipped. Simply cut the cord to the correct length, turn it back on itself, and whip it - several tight wraps of yellow thread.