Apparatus for forming a liquid-tight seal across gaps formed between adjacent components of a load-supporting surface useful at an outdoor worksite, the load-supporting surface being designed to support the weight of people, vehicles and equipment thereupon, the apparatus comprising: at least first and second mats arranged and adapted to be positioned adjacent to one another and releasably interconnected in the load-supporting surface, each said mat being configured to support the weight of people, vehicles and equipment thereupon and undergo movement relative to one or more other said mats without disengaging from the load-supporting surface, each said mat having an upper surface, at least a first side and an outer edge extending along said first side, each said mat further including an elongated channel formed in said upper surface thereof and disposed proximate to and extending at least partially along said outer edge thereof, wherein when said first side of said first mat is, in use, positioned adjacent to said first side of said second mat in the load-supporting surface, a gap is formed between said adjacent outer edges of said respective first sides of said first and second mats; and a liquid-impermeable, elongated seal member arranged and adapted to form a seal between said first and second mats across said gap to prevent the entry of liquid into said gap from said upper surfaces of said first and second mats, said elongated seal member being configured to be coupled to said respective elongated channels of said first and second mats, sealingly engage each of said first and second mats at one or more locations on each said respective mat other than said outer edge thereof and extend across said gap, said seal member being configured to move within said gap in response to movement of at least one of said mats without said seal member losing its sealing engagement with said first and second mats or disengaging from said elongated channels thereof; wherein said elongated seal member includes an elongated central body and first and second elongated legs (106,108) extending outwardly therefrom on opposite sides thereof, said central body being configured to extend at least partially into and to bend and flex within said gap; and characterised in that: each said mat includes at least one elongated recess formed in said upper surface thereof around said elongated channel, each said recess being configured to receive and sealingly engage one of said legs (106, 108) of said seal member and position said associated leg (106, 108) flush with or below said upper surface of said respective mat. at least first and second mats arranged and adapted to be positioned adjacent to one another and releasably interconnected in the load-supporting surface, each said mat being configured to support the weight of people, vehicles and equipment thereupon and undergo movement relative to one or more other said mats without disengaging from the load-supporting surface, each said mat having an upper surface, at least a first side and an outer edge extending along said first side, each said mat further including an elongated channel formed in said upper surface thereof and disposed proximate to and extending at least partially along said outer edge thereof, wherein when said first side of said first mat is, in use, positioned adjacent to said first side of said second mat in the load-supporting surface, a gap is formed between said adjacent outer edges of said respective first sides of said first and second mats; and a liquid-impermeable, elongated seal member arranged and adapted to form a seal between said first and second mats across said gap to prevent the entry of liquid into said gap from said upper surfaces of said first and second mats, said elongated seal member being configured to be coupled to said respective elongated channels of said first and second mats, sealingly engage each of said first and second mats at one or more locations on each said respective mat other than said outer edge thereof and extend across said gap, said seal member being configured to move within said gap in response to movement of at least one of said mats without said seal member losing its sealing engagement with said first and second mats or disengaging from said elongated channels thereof; wherein said elongated seal member includes an elongated central body and first and second elongated legs (106,108) extending outwardly therefrom on opposite sides thereof, said central body being configured to extend at least partially into and to bend and flex within said gap; and characterised in that: each said mat includes at least one elongated recess formed in said upper surface thereof around said elongated channel, each said recess being configured to receive and sealingly engage one of said legs (106, 108) of said seal member and position said associated leg (106, 108) flush with or below said upper surface of said respective mat.