欧州(EP)クレームにおいては、図面に記載の符号を、クレーム中の対応要素に付けた方が理解しやすい場合は丸括弧とともに付けなければならないとされており(Rule 43(7))、これは欧州特許実務において広く行われている。

Reference characters corresponding to elements recited in the detailed description and the drawings may be used in conjunction with the recitation of the same element or group of elements in the claims. The reference characters, however, should be enclosed within parentheses so as to avoid confusion with other numbers or characters which may appear in the claims. The use of reference characters is to be considered as having no effect on the scope of the claims.

The European Patent Convention
Rule 43(7)
Where the European patent application contains drawings including reference signs, the technical features specified in the claims shall preferably be followed by such reference signs relating to these features, placed in parentheses, if the intelligibility of the claim can thereby be increased. These reference signs shall not be construed as limiting the claim.