Most cases for disability are decided based on strength and postural limitations. How much can a person lift and carry? How long can a person sit, stand, or walk? Can the person bend, crouch, crawl, or stoop? Once the Administrative Law Judge determines a claimant's strength and postural limitations, those limitations are compared with the claimant's past relevant work and other jobs in the national economy.
What about the person that can perform most work tasks but has a medical condition that will prevent them from performing work on days when the condition flares up? Social Security had this situation in mind when it issued Social Security Ruling 96-8p, which states:
Ordinarily, RFC is an assessment of an individual's ability to do sustained work-related physical and mental activities in a work setting on a regular and continuing basis. A "regular and continuing basis" means 8 hours a day, for 5 days a week, or an equivalent work schedule."
In cases like this, the Administrative Law Judge will normally call a Vocational Expert to testify as to the allowable absenteeism per month. Usually, the Vocational Expert will testify that an employer will not allow an employee to miss more than two days per month if the job is a semi-skilled or unskilled job.