Retaining wall structures can consist of precast concrete, insitu reinforced concrete , a gabion wall or a proprietary system of precast concrete blocks or layers of steel mesh / plastic geogrid tied in as layers into the slope being retained. Retaining walls are used to provide soil retention and the design of these for large scale retaining structures will require detailed geotechnical information. The rear of retaining walls will normally be backfilled with a suitable free draining material and regular weep holes will be provided at the base of any solid wall to prevent water pressure developing at the rear of the reaintaing wall. Buried faces of retaining walls can also be protected with two coats of bituminious paint.  Anguila, Antigua, Argentina, Aruba, Australia, Austria, Bahamas, Bahrain Bangladesh Barbados Belgium Belize Bermuda Bolivia Bosnia Botswana Bouvet Brazil British Virgin Islands Brunei Bulgaria Cambodia Cameroon Canada Cayman Islands Chad Chile China Colombia Commoros Congo Cook Islands Costa Rica Croatia Cuba Curacao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Dutch Antilles East Timor Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands Fiji Finland France French Guyana French Polynesia Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadelupe Guam Guatemala Guyana Haiti Holland Hong Kong Hungary Iceland India Indonesia Iran Iraq Ireland Italy Jamaica Japan Jordan Kazakhstan Kenya Korea Kuwait Laos Latvia Lebanon Lesotho Liberia Libya Liechtenstein Luxembourg Macao Macedonia Madagascar Malawi Malaysia Maldives Mali Malta Marshall Islands Martinique Mauritania Mauritius Mexico Micronisia Monaco Mongolia Monserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia South Africa South Korea Spain Sri Lanka St Lucia St Maarten St Vincent Sudan Surinam Swaziland Sweden Switzerland Syria Taiwan Tanzania Thailand Tonga Trinidad Tunisia Turkey Turks United States America USA UAE United Arab Emerates Uganda Ukraine UK United Kingdom Uruguay US Virgin Islands New Zealand Nicaragua Niger Nigeria Niue Norfolk Island North Korea North Mariana Islands NI Northern Ireland Norway Oman Pakistan Panama Papua New Guinea Paraguay Peru Philippines Poland Puerto Rico Qatar Reunion Island Romania Russia Rwanda Saba San Marino Santo Domingo Sao Tome Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Slovakia Slovenia Solomon Islands Somalia Uzbekistan Vanuatu Vatican City Venezuela Vietnam  British West Indies Western Samoa Yemen Zaire Zamia Zanzibar Zimbabwe