Mechanical trap damage inflicted upon the wearer is reduced by 50%. They do not reduce magic damage of any kind, even from magical traps.
As long as the trap is mechanical, the effect from this item stacks with other point-based items that mitigate trap-damage, but not other items that reduce trap-damage by a percentage.
Mechanical Trap: a physical (non-magical) hazard that gets sprung on the party as they advance through the adventure.