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

appal

appeal

appear

appease

append

applause

apply

appoint

appraise

apprise

approach

approve

bopping

capping

chipper

chipping

chopper

chopping

clapper

clapping

clipper

clipping

clopped

clopping

copper

copping

cropper

cuppa

cupping

dapper

dappling

dipper

dipping

dripping

dropper

dropping

equipped

flapper

flapping

flippant

flipper

flipping

flopping

foppish

grappa

gripper

gripping

happen

hipper

hippest

hippo

hopper

hopping

kipper

lopping

mapping

moppet

mopping

napper

napping

nipper

nipping

oppose

oppress

pepper

pipped

pippin

pipping

poppa

popper

poppet

popping

propping

puppet

quipping

rappel

rapper

rapping

ripper

ripping

rippling

sapper

sapping

scupper

shipping

shopper

shopping

sipper

sipping

skipper

skipping

slapper

slapping

slipper

slipping

slopping

snapper

snapping

snippet

snipping

sopping

stepper

stepping

stopper

stopping

strapper

stripper

supper

supplant

supply

support

suppose

suppress

swapped

swapping

tapping

tippet

tipping

topper

topping

toppling

trapper

trapping

tripping

uncapped

untapped

unzipped

upper

upping

whippet

whipping

whopper

whopping

wrapper

wrapping

yapping

yipped

yuppies

zapper

zapping

zipper

zipping