This may not be a particularly lazy hack, as it actually involves a lot more work than if it were to be done the normal way. However, it is a hack all the same. If you are ever in a pinch and you need to mask some potatoes, if you don't have a masher or a fork, you can use a sieve and a spoon and just push it through for the "mashed" effect.
You have to make sure to cook the potatoes very thoroughly if you are using this hack. Otherwise, you'll never be able to get them to pass through the sieve.