AN alleged "serial predator" told one of his child victims to be quiet and threatened to violently rape the other during two failed kidnappings in Sydney, court documents allege.

The Sydney father and Wattyl paint salesman is also accused of using a yellow Stanley knife in one of the attacks.

Mark Anthony Hanson, 49, shook his head and mouthed the words "no way" during Parramatta Local Court proceedings on Monday, at which he was denied bail.

Detectives from Strike Force Middural arrested Hanson about 6.45pm (AEST) on Sunday at his Castle Hill house, in Sydney's northwest, and seized a number of items including a personal computer.

He is charged him with multiple kidnapping, child abduction and weapon offences relating to two incidents earlier this year.

Hanson allegedly grabbed a 14-year-old girl by the throat and threatened her with the Stanley knife on a footbridge at Westleigh, also in Sydney's northwest, in April.

"If you say anything or do anything I will f*** you really bad," he allegedly said.

She wet herself in fear but broke free and ran home to raise the alarm.

Police say Hanson also tried to snatch a six-year-old girl from her babysitter at netball courts in South Turramurra in February.

A woman who was waiting to meet friends at the courts noticed a man in a car slowly following the girl as she rode her scooter, the court documents say.

A short time later she heard a "short, young, piercing, scared scream" from behind a toilet block where she allegedly saw the man using both arms to hold the girl, whose head could be seen over his shoulder.

"Shhh, be quiet," the woman heard the man say to the girl.

The woman chased him into bush before he disappeared.

CCTV footage from the day of the Westleigh incident showed a Holden Commodore station wagon similar to the one issued to Hanson by Wattyl and the one seen at the South Turramurra incident.

Three days before his arrest, detectives matched DNA evidence found on the shirts of both victims to Hanson's DNA profile via a sample of his they obtained covertly.

The court documents say police "believe the accused is a serial predator who, if not located, would commit further offences".

His lawyer, Shaun Titmarsh, told the court that the case against Hanson was circumstantial and his client's parents and his 29-year-old son lived in Sydney.

Hanson's place of residence and his work commitments meant he frequently visited the areas where the incidents took place, Mr Titmarsh said.

He said his client was willing to forfeit $20,000 in surety to secure bail.

Hanson shook his head and said "no way" as police prosecutor Kate Young said he was a danger to the community and a flight risk.

Magistrate Alison Viney noted that Hanson had no prior convictions but refused bail and scheduled him to appear in the same court on September 6.

Outside court, Mr Titmarsh said his client was adamant he was not guilty of the offences.