Factbox: How Nigeria's elections should work in 2015

ABUJA (Reuters) - Here are some details of how Nigeria's presidential and parliamentary elections on Saturday will work. BIOMETRIC CARDS The Independent National Electoral Commission (INEC) registered 68.8 million voters, of whom 82 percent have picked up their voter cards. For the first time, Nigeria will use biometric cards to identify voters. INEC is introducing electronic card readers to the 155,000 polling stations to curb ballot-stuffing, rife in past polls. INEC will have polling units inside camps and other designated areas for the 1.5 million people displaced by Boko Haram who cannot go home. ACCREDITATION * All voters must register for accreditation at their assigned polling station between 8 a.m. (0700 GMT) and 1 p.m. * Accreditation ends when the last person who had joined the queue by 1 p.m. has been processed. * INEC officials will tap the PVC on a handheld smart card reader and then scan the voter's fingerprint. * Should the fingerprint scan fail after four attempts but the voter card is authenticated, the registered voter may still vote at the discretion of the INEC official after filling in an incident form and having their identity cross-checked. VOTING * Voting commences at 1:30 p.m. or whenever accreditation ends. * Voting continues until the last person has voted. Voters can remain outside at polling centers to observe counting. * Voters mark their ballots with a thumbprint next to their choice and put it in the box in front of an INEC official to ensure the ballots go into the corresponding boxes. RESULTS * The winning presidential candidate must secure a simple majority as well as at least 25 percent of the vote in two-thirds of the 36 states plus the federal capital territory. * The electoral commission says votes will be counted and announced publicly at each polling center and posted. * Copies of unit results will be uploaded to the INEC website. * If there are complaints, the information saved on the card reader will be used by the collation officer to decide the case. * If the total number of votes exceeds the number of accredited voters at a polling unit, all the votes for that center will be nullified to prevent ballot-stuffing and multiple voting. * The result will be announced by INEC after everything has been counted. Voting could continue on Sunday in polling units where there have been technical glitches. * A run-off for the presidency will be held within seven days after the result announcement if either the simple majority or state requirement is not met. SECURITY * INEC says there will be at least three security personnel at every polling station. * Soldiers will be positioned along roads but will not be allowed around the polling stations. * Vehicle movement will be banned between 8 a.m. and 5 p.m. on the election day. * Nigeria has also closed land and sea borders as of midnight March 25 until midnight of the election day. * Candidates will not be allowed into polling centers with armed personnel. They will be required to vote and return home and will not be allowed to circulate or visit other voting centers. INEC hopes this will reduce voter intimidation. (Compiled by Julia Payne; Editing by Tim Cocks)