Proper Mechanics

[stewcall]

This Rookie still sorting it all out
On the mechanics of a jump/held ball

A) It seems no one gives the open palm before they signal a held ball. I understand the need to stop people from mugging each other- just wanted to know what is proper

B) You and partner agree to deter an OOB call when you did not see the play. Once deferred- if the second (or third offical) did not see the play we agree to go with the arrow.
Once deferred, is the proper mechanic to signal a jump/held ball. Although this doesn't seem the proper call- it does seem to add less confusion to the table, coaches etc- to insure the arrow changes after the throw-in
Stew in Virginia (CVBOA)