Method of sealing the gap between adjacent mats in a reusable load-supporting surface deployed on the ground, the load-supporting surface capable of supporting the weight of vehicles and equipment thereupon and including at least two mats, each mat being planar and having at least four sides and an edge extending along each side, the first and second sides of each mat having a lower lip extending horizontally outwardly below the edge thereof and the third and fourth sides of each mat having an upper lip forming the edge thereof, the respective upper and lower lips of different mats being interconnectable with locking pins releasably securable through corresponding locking pin holes formed therein, wherein when at least two mats are used to form the load-supporting surface, the gap is formed between adjacent edges of adjacent mats, the gap having a width, depth and length and being in fluid communication with a horizontally-extending interface formed between the adjacent upper and lower lips of the adjacent mats, the interface being in fluid communication with the ground beneath the load-supporting surface, the method comprising: (a) placing a first mat on the ground; (b) placing an elongated seal member along the edge of the first side of the first mat so that a first side wall of the elongated main body of the seal member abuts that edge of the first mat and an elongated tail of the seal member extending outwardly from its main body extends across a portion of the lower lip of the first mat along its first side; (c) positioning the third side of the second mat adjacent to the first side of the first mat so that the edge of the third side of the second mat abuts a second side wall of the main body of the seal member and the upper lip of the third side of the second mat overlays the lower lip of the first mat and the tail of the seal member, wherein the main body of the seal member is sandwiched between the respective aligned edges of the adjacent mats and the tail of the seal member is sandwiched between the respective aligned upper and lower lips of the adjacent mats; (d) aligning at least one locking pin hole of the upper lip of the second mat over a locking pin hole of the lower lip of the first mat; and (e) securing a locking pin in the at least one aligned pair of respective locking pin holes of the first and second mats to compress the main body of the seal member between the first and second mats and into sealing engagement with the respective adjacent edges thereof, whereby fluid introduced onto the load-supporting surface is prevented from flowing from the gap into the interface formed between the first and second mats. (a) placing a first mat on the ground; (b) placing an elongated seal member along the edge of the first side of the first mat so that a first side wall of the elongated main body of the seal member abuts that edge of the first mat and an elongated tail of the seal member extending outwardly from its main body extends across a portion of the lower lip of the first mat along its first side; (c) positioning the third side of the second mat adjacent to the first side of the first mat so that the edge of the third side of the second mat abuts a second side wall of the main body of the seal member and the upper lip of the third side of the second mat overlays the lower lip of the first mat and the tail of the seal member, wherein the main body of the seal member is sandwiched between the respective aligned edges of the adjacent mats and the tail of the seal member is sandwiched between the respective aligned upper and lower lips of the adjacent mats; (d) aligning at least one locking pin hole of the upper lip of the second mat over a locking pin hole of the lower lip of the first mat; and (e) securing a locking pin in the at least one aligned pair of respective locking pin holes of the first and second mats to compress the main body of the seal member between the first and second mats and into sealing engagement with the respective adjacent edges thereof, whereby fluid introduced onto the load-supporting surface is prevented from flowing from the gap into the interface formed between the first and second mats.