Each of these points are general for fashionable bonnets made of straw, primarily straw plait, from approx 1858 through 1863. Finer points adjust with each season’s prevailing fashion.
General Construction – Straw bonnets were sewn by hand in the round. Plaits ranged from 1/8″ split straw to wider whole straw and fancy plaits. Woven straw was also used.
Tip – The back section of the crown in the tip. On a straw bonnet this can either be domed, flattened at the back curving to the side of the crown. It should not have a sharp angular transition from the back to the sides.
Crown – The crown of a straw bonnet should create a smooth transition from the crown to the brim. Much of the shaping in the bonnet will be created in this transition area.
Brim – The brim of a straw bonnet will vary according to fashion. The brim’s edge should be a single or double row of straw plait. It should not have raw edges needing to be bound.
Cheek-tabs – The cheek-tabs should have a gentle curve coming from the neck edge of the crown along the side of the bonnet dropping down to roughly your jaw line meeting the brim edge. This is a graceful line, not a straight edge or angular transition. There is a variation in the twist of the cheek-tab from the fifties into the sixties. The cheek-tab is part of what helps hold a bonnet in place.
Binding – The binding on a straw bonnet should be straw plait. Raw edges were covered on the exterior and sometimes the interior along the back of the cheektabs, sides and tip. Multiple rows were used as well.
Lining – A lining is a functional layer of light weight, open-weave cotton covering most of the interior of the bonnet. It aids in keeping the straw from snagging the hair while worn. The lining can not be seen when the bonnet is worn.
Frill/Cap/Ruche –This decorative layer of gathered cotton or silk covers fills the inside of the brim. This is very fine most often net, lace or organza. The full frill aides in holding the bonnet in place.
Facing – Some bonnets have a facing of silk from the edge of the brim through the first couple inches of the interior brim.
Bavolet/Curtain – The bavolet is attached to the binding edge on a straw bonnet along the sides and crown. This silk piece should be lined with net to give it more body. The bavolet may be a single piece of fabric, most often on the bias and occasionally on the grain, or pieced from bias cuts of ribbon. The bavolet may also be decorated.
Functional Ties – The functional ties are attached to the interior of the cheek-tabs or under the decorative ties. These are narrower ribbon to hold the bonnet in place.
Decorative Ties – Decorative ribbons are wide, 3″-8″ based on a wide survey I did years ago. They are on the grain, not bias. Tied, they do not take the support of the bonnet.
Interior Decoration – Interior decoration also helps hold the bonnet in place.
Find the earlier video on Bonnet Stays here: https://youtu.be/gcnLtlDGblk
If I Had My Own Blue Box: 
Thank you so much for talking about the double ribbon ties. Every bonnet I have bought only has 1 set of ties! I suppose I’ll be adding the extra actual tying/keeping on your head ribbons now. LOL That’s been the most “mysterious” piece to me! &, that the bavolet has a stiffer lining to keep it “poufed” up. After trying to decorate a bonnet myself, this helps immensely! Thank you so much for these truly informative videos!!!