Demonstration vernier

Two pieces of tongued and grooved floor board about 1 m long can be used to make this apparatus. Saw 7 cm off the tongued board and glue it into the groove to give an end stop. With Indian ink or saw cuts, mark off graduations 5 cm apart along the whole length of the longer board. Use about 50 cm of the tongued board to provide the vernier slide.  Graduate it  by measuring 45 cm  from  one end  and  in-between this into ten equaparts, i.e. 4.5 cm each. The remaining piece of board cans beused to give brackets so that the apparatus will stand vertically on the bench.