A pair of drawing compasses (10) comprises a first leg (11) having a spike (14), a second leg (12) hinged to the first leg (11), and an implement holder (20) attached to the second leg (12). The holder (20) comprises a partly externally threaded portion (21) extending transversely away from the second leg (12) and comprising a mounting hole (22) into which an implement (e.g. a pencil) may be inserted, and a complementarily internally threaded clamping ring (30) which is rotatable on the external thread so as to enable it to be moved axially across the hole (22) to clamp the implement in the hole (22). The pitch of the threads lies in the range 2 to 5 turns per cm and/or the helix angle of the threads lies in the range 12 DEG to 5 DEG , so permitting rapid frictional clamping of the implement. The internal thread (31) of the clamping ring (30) comprises fractionally less than one turn. IMAGE
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