Walls of brick, block or concrete do not take kindly to normal long picture hook pins.
Toly moulded hooks have short hardened steel pins pre-loaded. These are hammered into the wall surface. They are designed for use where the plaster is very thin, so that most of the length goes into the wall material. Wall surfaces vary, so always check before hanging a picture.
Use cord not wire. Do not use these hooks for heavy or valuable pictures or where items below might get damaged.