Quantity   Component name
1 × carriage 3D-printed part
1 × back plate 3D-printed part
1 × retaining clip (optional) 3D-printed part
2 × rails 48mm length plain steel rod, tapped at ends to M3
1 × various M3 screws/locking nuts
1 × spring large enough diameter to slip over rail(s), e.g. from ballpoint pen
1 × Graphtec CB09 cutter or similar + blades
1 × cutting mat to save your printer's bed from getting cut up