Wikipedia
As-Sirāt is, according to Islam, the hair-narrow bridge which every person must pass on the Yawm ad-Din ("Day of the Way of Life" i.e. Day of Judgment) to enter Paradise. It is said that it is as thin as a hair and as sharp as the sharpest knife or sword. Below this path are the fires of Hell, which burn the sinners to make them fall. Those who performed acts of goodness in their lives are transported across the path in speeds according to their deeds leading them to the Hauzu'l-Kausar, the Lake of Abundance.
Muslims who offer the obligatory prayers (Fajr, Dhuhur, Asr, Maghrib, Isha) and recite the Surah Al-Fatiha, which is a supplication in which they ask God to guide them through the righteous path, has been called by scholars a precursor to the as-Sirāt.
Narrated by Abu Sa'id Al-Khudri: We, the companions of the Prophet said, "O Allah's Apostle! What is the bridge?' He said, "It is a slippery (bridge) on which there are clamps and (Hooks like) a thorny seed that is wide at one side and narrow at the other and has thorns with bent ends. Such a thorny seed is found in Najd and is called As-Sa'dan. Some of the believers will cross the bridge as quickly as the wink of an eye, some others as quick as lightning, a strong wind, fast horses or she-camels. So some will be safe without any harm; some will be safe after receiving some scratches, and some will fall down into Hell. The last person will cross by being dragged over the bridge." (Sahih Bukhari- Volume 9, Book 93, Number 532)
The Chinvat bridge in Zoroastrianism has many similarities and is a close concept to As-Sirat.