Abstract: A sheet of material 2 which can be incorporated into a booklet has an adhesive strip 5, foldable portion 7 and first and second perforated fold 8a and 8b. Information can be entered into the space delimited between the first and second perforated folds 8 and 10 and concealed by removing a protective paper 6 from the adhesive strip 5 and folding the foldable section 7 at perforated folds 8, such that it sticks to the adhesive strip 7 and conceals information in space 9. The perforated folds 8 and 10 delimit and create a detachable strip 11 which can be torn away in order to reveal the information in space 9 when required.