Hat Stand is an addon to the Hats Mod. You require that to be installed before this can work.
Why an addon?
– Hats is compatible on servers without it. This on the other hand, is not.
Hat Stand mod adds a single block item, a Hat Stand:
Servers require Hat Stand mod to be installed before the client can use it. Ignoring this advice may lead to crashes.
Download Hat Stand Addon for Hats Mod and Minecraft: