(5) (a) Where the application contains drawings, the technical features mentioned in the claims shall, as far as possible, be followed by the reference signs relating to such features, and when used, the reference signs shall be placed between parentheses. (b) Where inclusion of reference signs does not particularly facilitate better understanding of a claim, it should not be made. (6) Any claim submitted after the filing date of the application and which is not identified with the claims previously appearing in the application shall, at the choice of the applicant, be submitted either as a new claim or as an amended claim, together with the appropriate fee specified in regulation 10(4) or 23. (7) The deletion of any claim previously appearing in the application shall be made by indicating the number of the previous claim followed by the word "cancelled" 13. (1) Any drawings forming part of an application for a patent shall be on writing sheets, the usable surface area of which shall not exceed 26.2 centimetres by 17 centimetres. (2) The sheets shall not contain any frame round the usable or used surface and the margins shall be - (3) (a) 2.5 centimetres at the top; (b) 2.5 centimetres on the left side; (c) 1.5 centimetres on the right side; and (d) 1.0 centimetre at the bottom. A drawing shall be done -