Reciprocating or reversing screw n nut
The screw is specially manufactured with a special nut to reciprocate at its travel ends.
RS1010-200 10mm pitch 200mm working length 400mm total
RS2020-250 20mm pitch 250mm working length 430mm total
RS2525-500 25mm pitch 500mm working length 700mm total
It's different with a normal lead screw or ball screw which is one direction no return running except you change the motor from CW to CCW vice versa.
2020 Reversing Screw Block
2525 Reversing Screw Block