A surgical instrument (100, 200), comprising: a device having a functional end configured to be inserted into a body part; a shaft coupled to a proximal end of the device; a shaft housing having a proximal end configured to receive a distal end of the shaft and operable to move along a central axis of the shaft; a tube coupled to the distal end of the shaft housing and configured to partially house the device such that the functional end of the device at least partially extends beyond the distal end of the tube; a plurality of arcuate levers (210, 210a, 210b, 210c), each arcuate lever having a proximal end coupled to the shaft and a distal end coupled to the shaft housing such that pressing one or more of the plurality of arcuate levers moves the shaft housing and the tube toward the functional end of the device, causing the tube to transition the device from a deactivated state to an activated state; the proximal end of each of the plurality of arcuate levers comprises a lever tail configured to rotate within a tail housing of the shaft; and the distal end of each of the plurality of arcuate levers comprises a lever head configured to rotate within a head housing of the shaft housing; wherein pressing the one or more of the plurality of arcuate levers causes the lever tail and the lever head of each of the plurality of arcuate levers to rotate within the respective tail housing and head housing, and characterised in that the shaft comprises a plurality of protrusions extending outward from the central axis of the shaft; and the shaft housing comprises a plurality of receptacles on an interior thereof, each receptacle configured to receive one of the plurality of protrusions when the shaft is received by the shaft housing, such that, when the one or more of the plurality of arcuate levers (210, 210a, 210b, 210c) are pressed, interaction of the respective plurality of protrusions and plurality of receptacles allows the shaft housing to move along the central axis of the shaft toward the functional end of the device in correspondence to a length of the one or more of the plurality of arcuate levers while limiting rotation of the shaft relative to the shaft housing. a device having a functional end configured to be inserted into a body part; a shaft coupled to a proximal end of the device; a shaft housing having a proximal end configured to receive a distal end of the shaft and operable to move along a central axis of the shaft; a tube coupled to the distal end of the shaft housing and configured to partially house the device such that the functional end of the device at least partially extends beyond the distal end of the tube; a plurality of arcuate levers (210, 210a, 210b, 210c), each arcuate lever having a proximal end coupled to the shaft and a distal end coupled to the shaft housing such that pressing one or more of the plurality of arcuate levers moves the shaft housing and the tube toward the functional end of the device, causing the tube to transition the device from a deactivated state to an activated state; the proximal end of each of the plurality of arcuate levers comprises a lever tail configured to rotate within a tail housing of the shaft; and the distal end of each of the plurality of arcuate levers comprises a lever head configured to rotate within a head housing of the shaft housing; wherein pressing the one or more of the plurality of arcuate levers causes the lever tail and the lever head of each of the plurality of arcuate levers to rotate within the respective tail housing and head housing, and characterised in that the shaft comprises a plurality of protrusions extending outward from the central axis of the shaft; and the shaft housing comprises a plurality of receptacles on an interior thereof, each receptacle configured to receive one of the plurality of protrusions when the shaft is received by the shaft housing, such that, when the one or more of the plurality of arcuate levers (210, 210a, 210b, 210c) are pressed, interaction of the respective plurality of protrusions and plurality of receptacles allows the shaft housing to move along the central axis of the shaft toward the functional end of the device in correspondence to a length of the one or more of the plurality of arcuate levers while limiting rotation of the shaft relative to the shaft housing. wherein pressing the one or more of the plurality of arcuate levers causes the lever tail and the lever head of each of the plurality of arcuate levers to rotate within the respective tail housing and head housing, and characterised in that the shaft comprises a plurality of protrusions extending outward from the central axis of the shaft; and the shaft housing comprises a plurality of receptacles on an interior thereof, each receptacle configured to receive one of the plurality of protrusions when the shaft is received by the shaft housing, such that, when the one or more of the plurality of arcuate levers (210, 210a, 210b, 210c) are pressed, interaction of the respective plurality of protrusions and plurality of receptacles allows the shaft housing to move along the central axis of the shaft toward the functional end of the device in correspondence to a length of the one or more of the plurality of arcuate levers while limiting rotation of the shaft relative to the shaft housing.