A bedside rail is fitted to the bed, so the work starts at the bed. Do it on a day when you can take your time, not at 3am, and do it with the mattress she really sleeps on, not the one in the showroom photo.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Stop 1: Measure before you attach anything
With the mattress at its normal height, measure from the floor to the top of the mattress at the edge where she gets up. Write that number down. Measure the bed frame, the platform or box spring, and the mattress thickness separately, because the rail often clamps to the frame, not the mattress. Note which side she exits and whether the nightstand or wall limits how far the rail can sit.
Then open the instructions for the rail you have and compare its height and gap figures to your numbers. Do not work from memory or from the box. Public safety guidance on bed rails warns about gaps where a head, neck, or limb can become trapped, so the gap figures are the ones to trust. You can check the public guidance listed on the sources page.
Stop 2: Check the gap before you tighten anything
Measure the space between the rail and the mattress at both ends and in the middle. Measure any space between the rail and the bed frame. If any gap is wider than the instructions allow, or if a gap appears when the mattress is pressed down at the edge, stop and change the setup before tightening. Do not fill a gap with pillows or blankets to make it look closed.
Ask the physician or the occupational therapist whether a bed rail is the right tool for her at all. A rail can help some people get up and can make others reach, climb, or lean in ways that add risk. That is a clinical question, and it belongs with her care team.
Stop 3: Set the height so she pushes up, not over
Set the top of the rail so that, when she sits on the edge of the bed, her hand meets it at a comfortable height without reaching far or leaning forward. Test this from a seated position, because a rail set for a person standing can be too high or too low for the person sitting. Lock every height adjustment as you go, then recheck it once the setting is done.
Stop 4: Test it the way she moves
With you standing close and her sitting on the edge, have her take hold, stand, and let go. Then have her sit back down. Watch the bed, not only the rail. If the bed frame shifts, the rail rocks, or a clamp slips, stop using it and fix the mounting before the next move. Push the top of the rail gently in each direction. Any movement you can feel by hand means it is not yet secure.
Repeat the test at night only after the daytime test passes, and keep a lamp on the bed-to-bathroom route while you test.
Stop 5: Write down what you set
Keep a card in the drawer with the mattress height, the rail height above the mattress, the gap at each end and in the middle, the mounting points used, and the name of the person who fitted it. Add the name of the person who checks the clamps and the gaps each week. If the mattress is replaced later, the card tells the next person what has to be measured again before the rail is used.