Consider a block of mass .m. connected to a thread which runs over a pulley and the other end of it is connected to a pan. If we keep on adding small weights, the block does not start sliding at the first attempt. The block starts moving only when the weights in the pan balance and are slightly greater than the frictional force (limiting friction) between the block and table. since static friction itself will change or self - adjust to provide an equal and opposite force till the force applied to the object is less than or equal to maximum static friction .
