conversely as shown in fig6 when the latch 62 is positioned in locking position the base 64 rotates away from the second side wall 36 and towards the tongue 48 such that the corner 78 overlies the lip 56 in this position the first coupler 22 is retained within the second coupler 23 it will be appreciated that in the embodiment illustrated in fig5 and 6 the notch 41 is sized such that portions of the front wall 30 overlie portions of the second side 68 of the latch 62 when the latch is pivoted between the locking and the unlocking positions in this way the entire opening 74 of the latch 62 is enclosed within the second coupler 23 and debris is prevented from entering the opening 74 to possibly interfere with the operation of the spring 76 it will be further appreciated that portions of the second side 68 of the latch 62 adjacent the notch 41 extend outwardly from the notch 41 when the latch is pivoted between the locking and the unlocking positions the embodiment shown in fig7 and 8 and designated by reference character 20a is similar to the embodiment 20 shown in fig5 and 6 except that portions of the front wall 30 completely overlie the second side 68 of the latch 62.