Information on string ceremony I once attended a puja at a Sri Lankan temple where a string was passed around during chanting. Afterwards the monks tied string around our wrists and poured water over our heads. What is the string called? Any explanation on the significance. I notice some people kept the string on for months, others said to cut it off at the end of the day.
While the recital continues there will be found a pot of water placed
on a table before the monks. On this table there is also a sacred
thread (pirit nula). For an all night pirit ceremony the casket
containing a relic of the Buddha, and the Pirit Potha or The Book of
Protection written on ola leaves, are also brought into the pavilion.
The relic represents the Buddha, the &quot;Pirit Potha&quot; represents the
Dhamma or the teachings of the Buddha, and the reciting Bhikkhu-Sangha
represent the Ariya-Sangha, the arahant disciples of the Buddha.
The thread is drawn round the interior of the pavilion, and its end
twisted round the casket, the neck of the pot of water, and tied to
the cord of the ola-leaf book. While the special discourses are being
recited the monks hold the thread. The purpose is to maintain an
unbroken communication from the water to the relic, to the Pirit Potha
and to the officiating monks, (Buddha, Dhamma, Sangha, the Ti-ratana,
the three jewels.) A ball of thread connected to &quot;The Three Jewels&quot;
and the water, is unloosened and passed on to the listeners (seated on
the ground on mats), who hold the thread while the recital goes on.
When the recital in Pali of the entire book is over at dawn, the
thread sanctified by the recital is divided into pieces and
distributed among the devotees to be tied round their wrists or necks.
At the same time the sanctified water is sprinkled on all, who even
drink a little of it and sprinkle it on their heads. These are to be
regarded as symbols of the protective power of the paritta that was
recited. It is a service of inducing blessings. It has its
psychological effects.
Dr. Bernard Grad of McGill University in Montreal painstakingly proved
that if a psychic healer held water in a flask and this water was
later poured on barley seeds, the plants significantly outgrew
untreated seeds. But — and this is the intriguing part — if depressed
psychiatric patients held the flasks of water, the growth of seeds was
retarded. Read more...

The practice of giving Paritta threads was even done by Pacceka Buddhas in the past.
It's basically used as a symbol of protection. There's no real time limit to how long you have to wear it. If it's clean, you can keep it as long as you want. It can be helpful in many ways. If you feel afraid, you can look at the thread and remember the Paritta chanting event. Remember taking refuge. And feel confident that you are able to handle any situation since you have the protection of the Triple-gem. Wearing the thread can make you disinclined to break precept. ex: &quot;Am I really going to kill while wearing this which represents the Triple-gem?&quot;, &quot;Am I really going to misbehave while wearing this sacred thread?&quot; etc.
Wearing a thread or a band for such reasons is much more wholesome than wearing bands/bracelets to make a fashion statement.