holds a washer 40 in place on the grating 100 and when tightened secures the grating 100 to the plate 102 fig5 a 7b as shown in fig6 a 6 b and 7 a the washer 40 is sufficiently wide to contact two spaced apart parts 106 of the grating 100 as shown in fig7 a the primary bolt 20 has a head 24 sized to fit snugly between bases 101 of the parts 106 optionally such a bolt head can be smaller so that there is no such snug fit fig8 illustrates the amount of total area of a grating 110 with spaced apart grating members 112 covered by washers 40 a like the washer 40 fig1 around bolts 30 a of apparatuses according to the present invention for example with a grating 110 which has an area as viewed from above as in fig8 of about one square meter six apparatuses are used according to the present invention the grating 110 has connection members 114 connecting the grating members 112 fig9 a and 9b show another embodiment of an apparatus according to the present invention the apparatus 90 according to the present invention is like the apparatus 10 fig1 and like numerals indicate like parts a primary bolt 92 has a body.