Ferrule: 14 x 23 mm Security Stud: 16 x 25 mm features: Sash window security stop set Window can be locked closed, or in open position for ventilation. Set includes two security studs and four ferrules Keys to be ordered separately code 75173 - see related products INSTRUCTIONS FOR USE Step 1 Drill 4 holes using a 10mm drill Two either side of window internally 100mm and 150mm above centre rail Step 2 Using a screwdriver fit screws into holes so that the heads of the screws are flush with window frame. Step 3 Replace stud into screw using key 75173 If ventilation is required use top screw so that window can be opened slightly whilst still being locked