The Heist Kit inserts have been designed to fit in the Burgle Bros box in a specific configuration.
Below is a top down shot of the inside of the box, showing the positioning of the Cops and Robbers box along the side (bottom of the picture). In the picture you can see that the floor tiles are in two equal sized stacks against the Cops and Robbers box. The rest of the cards are oriented sideways and at the end (right side) of the box.
After setting up the box as shown above, the Burglars’ Tool Bag is positioned on top as shown below.