You say you want to make 1 mesh out of the objects? That would remove all limb data and you would be better off to just make it out of 1 box. If you want to make it into 1 object however, you can use limbs.
sync on:sync rate 0
backdrop on
make object box 1,10,100,0
make object box 2,10,0,10
make mesh from object 1, 1
make mesh from object 2, 2
delete object 1
delete object 2
make object 1, 1, 0
for i = 1 to 3
add limb 1, i, 1
next i
for i = 4 to 5
add limb 1, i, 2
next i
delete mesh 1
delete mesh 2
rotate limb 1,0,0,90,0
rotate limb 1,2,0,90,0
offset limb 1, 0,5,0,5
offset limb 1, 2,-5,0,5
offset limb 1, 3,0,0,10
offset limb 1, 4,0,50,5
offset limb 1, 5,0,-50,5
color limb 1, 0, rgb(255,0,0)
color limb 1, 1, rgb(0,255,0)
color limb 1, 2, rgb(0,0,255)
color limb 1, 3, rgb(255,255,0)
color limb 1, 4, rgb(0,255,255)
color limb 1, 5, rgb(255,0,255)
do
CONTROL CAMERA USING ARROWKEYS 0, 0.1, 0.09
sync
loop