Usually after “short” vowels in words of more than one syllable.

ebb

abbess

abbot

babbling

blabbing

blobbing

blubber

bobbin

bobbing

bubbler

bubbling

clobber

clubber

clubbing

cobber

cobbler

cribbing

dabbing

demobbed

dobber

dobbin

drabbest

dribbling

drubbing

dubbing

fibber

fibbing

fobbing

gibbon

gibbous

gobbet

gobbler

gobbling

grabbing

grubber

grubbing

hobbit

jabber

jabbing

lobbing

lubber

mobbing

nibbler

quibblers

quibbling

rabbi

rabbit

ribbing

ribbon

robber

robbing

rubber

rubbing

rubbish

sabbath

scabbard

scribbler

scrubber

scrubbing

slobber

snobbish

snubbing

sobbing

squabbled

stabbing

stubborn

swabbing

throbbing

webbing

wobbling

yabby

yobbo