Many people think of landmines as round, platelike objects. In reality, mines come in a wide variety of shapes and sizes, depending on their application and the technology available.

Here is a great resource for learning more about all the different types of mines

From the above-mentioned site, here is a description of a PP-Mi-D anti-personnel mine from the Czech Republic:

The PP-Mi-D is a rectangular, wooden bodied A pers mine which is designed to wound or kill by blast effect. The design is based on the Russian PMD-6 A pers mine. The mine is basically two over lapping wood boxes which are connected clamshell style. The upper section acts as the pressure plate, and the lower section contains the fuze and 200 g TNT charge. The fuze is the Ro-1 pull fuze (MUV copy) which is equipped with a winged pin for pressure removal. Due to its wooden construction and expedient nature the PP-MI-D body will rot, thereby limiting its operational endurance. The fuze, however, may remain operational for a considerable time. As a result the mine may not detonate when pressure is applied to it, but may actuate if the mine is lifted. The PP-Mi-D can be located using metal detectors under most field conditions, and it can be defeated by blast overpressure from explosive breaching systems such as the Giant Viper and MICLIC.