the focus of this case study was to determine the impact of the co-construction and use of the clock model in the development of fractional understanding in a grade 4/5 classroom. a pretest, instruction, midtest, intervention, posttest, retention test sequence was used. the teaching unit was developed to address six areas of student difficulty with fractions identified in the literature: factional parts are equal size portions, fraction symbols, improper fractions, size of unit fractions, estimation and comparison, and equivalent fractions. the clock model was co-constructed by the 世界杯2022赛程表淘汰赛 with the teacher in the second half of the unit. 世界杯2022赛程表淘汰赛 used the clock model in four different forms: as an area model, as whole numbers of minutes, as equivalent fractions, and as an open clock. although some 世界杯2022赛程表淘汰赛 did not adopt the clock model, others used it with great success. most 世界杯2022赛程表淘汰赛 moved beyond using only landmark fractions of an hour to being able to work with thirds and sixths of an hour. the clock model helped some 世界杯2022赛程表淘汰赛 to better understand the relationship between equivalent fractions. recommendations are discussed.