DAY tickets for this summer’s Sonisphere 2011 Festival at Knebworth House will go on sale later this month – via a ballot scheme.

The three-day rock and metal event returns to the grounds of the Hertfordshire stately home from Friday, July 8 to Sunday, July 10.

Metallica top the bill on the opening day as part of the Big 4 Friday, with Biffy Clyro and Slipknot the other headliners over the weekend at the legendary rock venue.

Until now, festival-goers could only buy weekend passes to the UK leg of the international touring festival at Knebworth.

Demand for day tickets has been very high though, and organisers have made a limited number available through a ballot system.

To stand a chance of getting a ticket, fans have to register at the Sonisphere Festival website – see the link on the right.

Music-lovers have to sign up by midnight on Sunday, May 22, when the ballot closes.

Successful applicants will be notified which days they can purchase tickets for via email on May 25.

With weekend passes selling better than last year, a statement from Sonisphere promoters Kilimanjaro Live said: “In response to an overwhelming number of requests, we have been able to secure permission to put a strictly limited number of day tickets on sale via The Power Ballot scheme.

“Due to the huge demand for day tickets anticipated, and the limited number that can be made available, we have decided to use a ballot system as we believe it is the fairest way to ensure that everyone has an equal opportunity to obtain tickets.”

Metalheads can apply for as many days as they like to increase their chances, although full weekend tickets work out much cheaper than three separate day tickets.

Each customer may purchase up to four tickets for their allocated day. Tickets will be �80 per day, plus booking fee.

The day splits for Knebworth have also been confirmed, broken down stage by stage.

Thrash metal’s Big 4 of Metallica, Slayer, Megadeth and Anthrax will play the main Apollo arena stage on the Friday.

Scottish rockers Biffy Clyro will headline the Saturday night, with Weezer, You Me at Six, All Time Low and The Mars Volta also on the bill.

Masked Iowa metallers Slipknot will close proceedings on the Sunday, with comedian Bill Bailey headlining the Saturn outdoor stage.

The Sunday line-up also includes the likes of Limp Bizkit, Motorhead, Mastodon, Opeth and Airbourne.