Prior to the widespread availability of smokable crystal meth, snorting meth was pretty much the most popular method of ingesting the drug. Even crystal meth could be cut up or pulverized to reduce it to a powder suitable for snorting. Once chopped up into a fine powder, the meth is then snorted deeply into the nasal cavity using a straw, tube, or to be really glamorous, a rolled up bill. Once the meth is ingested, it's absorbed through the thin membrane of the nasal passages and similar to cocaine, will cause damage to the delicate membranes, sometimes causing permanent damage.
The onset of the high when snorting meth is typically between two and five minutes with a steep curve. Depending on the length of line snorted and its purity, this method will also induce a "rush" but not as intense as by smoking or injection.
Those who share their meth straws or meth snorting tubes with others are actually at risk of spreading infections such as the common cold or flu as well as other infections.