what type of thumb though? or should i say features? pretty wide options out there....
some that are permenatly mounted. or atleast the main frame of the thumb is, were you can then use some pins, that pull out to drop thump completely off. to others were mounts are welded or bolted rather good to the BH.
some thumbs are non adjustable. others have holes were thumb can be placed and perhaps at different angles.
and yet still some thumbs that are fully hyd thumbs with a hyd cylinder. to automatically adjust thumb as needed.
some thumbs are built heavy duty for larger industrial equipment, while others are cheaper / less heavier duty metal that are made to work for smaller size tractors for the weekend warriors / diyer's vs paying day job setups. BH can only lift so much weight added weight of thumb can be a "ugly thing" pending on next job / project you will have for the backhoe. example pulling posts, to actually digging a trench or like, i doubt you want thumb in the way. then when its time to clean up woods or firewood or what not tossing thumb back on easily.
i know there are some good diy builds here on the forum for thumbs. might suggest....
goto to
Google
type in without quotes.... "thumb site:tractorbynet.com"
then in the top bar of google clicking on "images"
above will only search this site, and bring back pictures/images that have pages with "thumb"