Introduction Vernier calipers can measure external dimensions using the pictured lower jaws. The Vernier calipers model has an object (Blue) for the internal jaws to measure width of an object with slider to control width of the object and simple drag action to control position of object. a slider for zero error slider checkbox for hint to scaffold the learners attention and point of focus checkbox for answer to show the meaning of reading on the main scale and the vernier scale with zero error calculations if any. drop down menu of the various common vernier scales for sense making and additional testing out by learners their ideas of how vernier works. fine <> control buttons for learners to manipulate the model with single incremental precision slider control for fast changes in the vernier measurement reset button to bring simulation back to original (default) setting.