Buy Wickes Twin Slot Flex Bookends mm 2 Pack online at freeonlineslotgamesplayforfun.review We supply trade quality DIY and home improvement products at great low prices. Book Ends White x mm 2 Pack () . RB UK Twin Slot Uprights White x 25mm 2 Pack (). Product rating: out of 5 stars. (52). This system comprises of wall fixed " twin " slotted uprights and sturdy brackets which " slot " into the upright as shown in the system images above. No Special.