Building adjustable shelves may be accomplished in several ways. Depending on the desired look, strength requirements and available materials, you may prefer one method over the others. To make adjustable shelving, the process essentially involves adding cleats, cutting notches or installing removable brackets into the vertical sides of a bookcase, cabinet or other enclosure. The benefit of making adjustable shelves is that shelf planks may be removed or reconfigured to accommodate shelf contents of all sizes. Whatever the preferred method, the result should be a series of closely-spaced cuts, notches or holes, providing you with the most adjustment options. Picking an inexpensive method, you will learn how to install removable metal brackets in a cabinet.
Step 1: Pre-Cut Cabinet Lumber
Assuming you are building the shelves from scratch, the first step is to pre-cut each piece of a bookcase, cabinet or other shelf-containing unit. Measure and cut the sides, top, bottom and back of the cabinet to size. Do the same for each shelf plank, making sure each fits within the parameters of the exterior pieces. Don't assemble anything yet, though. First, the holes must be drilled.
Step 2: Measure and Mark the Intervals
It is imperative that the two vertical supports be measured and marked equally, or else the shelves will not sit perfectly level. On one side of both vertical pieces you will drill a series of evenly-spaced holes in two columns. Each hole should align with the corresponding hole in the other column as well as with the opposite side piece. Use a T-square to draw straight, horizontal lines across the board as you measure down in even intervals. If you plan on drilling 20 holes per column, draw that many lines across each side piece with an equal distance between them.
Step 3: Draw Vertical Markers
With the horizontal lines in place, you need to next draw two vertical lines down each side indicating the position of the columns of holes relative to the edges of each board. A longer straightedge can accomplish this. The spacing between each column will depend on the width of the shelves. The resulting holes should be nearer the edges of the shelf plank than the center. Again, make sure each vertical line perfectly aligns with those on the opposite side.
Step 4: Drill Holes
A drillpress is handy for this step, for it can be set to only lower so far, making each hole the same depth. A handheld power drill will work too, only you have to be careful not to drill through the other side of the board. Drill a hole at every point of intersection between the two vertical lines and horizontal lines on both side pieces. Be sure to use the drill bit appropriate to the size of the mounting bracket.
Step 5: Assemble Shelf
Now that the holes are in place, it's time to assemble the cabinet or shelf. Join the sides with the top and bottom, and attach the back if present. Finishing the cabinet involves several other steps detailed elsewhere.
Once constructed, place four brackets, two per side into the corresponding holes. When in place and level, position each shelf plank and adjust if necessary.