Born April 26, 1926, in Houston, Texas, Ruby Kless Sondock attended Cottey College in Nevada, Missouri, for two years before marrying Lt. Melvin A. Sondock in Houston, Texas, in 1944. Years after having a family, Sondock attended the University of Houston Law Center and graduated as valedictorian of the 1962 law class. She was admitted to the Texas State Bar the year before her graduation from law school. Following law school, Sondock practiced law for seven years. Gov. Preston Smith appointed her judge of Harris County Domestic Relations Court No. 5 in 1973, making her the first woman in Harris County to hold a district level judgeship. She held the position for four years until Gov. Dolph Briscoe appointed her in 1977 to the 234th District Court; she became the first woman to hold that distinction in Harris County.
Sondock was appointed to the Texas Supreme Court by Gov. William P. Clements following the death of associate justice James G. Denton, who died of a heart attack on June 10, 1982. When the fifty-six year old Sondock was sworn in on June 25, she became the first woman justice on the court since 1925, when a special all-woman court served briefly to hear a single case involving the Woodmen of the World. Sondock completed Denton's term, which ended December 31, 1982, and did not seek election. Instead she returned to the 234th District Court, to which she won reelection without opposition the following November.
Following her judicial service, Sondock began working as a private mediator in Houston. Her alma mater, the University of Houston Law Center, hosts a biennial lecture series in her name, "The Ruby Kless Sondock Lecture in Legal Ethics."