| 摘要 |
A pad device includes a hole formed in the edge portion for engaging with a screw. A board has an opening engaged with the screw and has two legs and a gap formed between the legs. The legs each has a recess formed in the bottom portion. A knob is threaded to the screw for securing the board to the pad. A rule has a shaft engaged in the recesses of the legs such that the rule may rotate relative to the board and such that the rule may be disengaged from the pad when the board is secured to the pad. The rule includes one or two edges each having a metal strip for protecting the rule from being cut.
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