It will either suck them out or they will stick to the end - i have found the biggest obstruction is either a tennis ball or golf ball, or weeds growing in the downspout
Gutter spike to remove weeds or powerpole and pressure washer, i have a drain cleaning nozzle and i have fed this up the downspout and blown out.
Some guys just pressure wash muck out , benefit of gutter vac is all the muck is collected.
I am still perfecting best methods- but each job has different challenges -
hopefully over the next few weeks i will be in a position to tackle even the most demanding tasks.
One job i picked up a dart which fell to the ground- since purchase a hard hat
regards
Billy