Put the two objects in the same shape, and then do a horizontal concatenate:
julia> hcat(check1, reshape(check2, 4, 1, 2))
4×4×2 Array{Float64,3}:
[:, :, 1] =
0.236033 0.488613 0.251662 0.751313
0.346517 0.210968 0.986666 0.644883
0.312707 0.951916 0.555751 0.0778264
0.00790928 0.999905 0.437108 0.848185
[:, :, 2] =
0.424718 0.251379 0.0769509 0.0856352
0.773223 0.0203749 0.640396 0.553206
0.28119 0.287702 0.873544 0.46335
0.209472 0.859512 0.278582 0.185821
This is not what you were expecting, but I do think you copy-pasted your expectations wrong, as the same column is used two times (and the other is not used).