amfoto1 Loc: San Jose, Calif. USA

Are you certain those are Canon hoods? There are cheaper third party "clones" from a number of sources, often using the same model number. Sometimes those are fine, sometimes they don't fit very well. Depending upon who you bought from, they might have substituted a clone.

Also, if Canon (and probably most clones), are you absolutely certain you have them fully clicked into place?

I have 18 Canon lenses and use hoods on all of them, all the time. The only one I have that's loose is a "clip on", which some of the older design lenses use (mine is a Canon EF 85mm f/1.8 USM). I've knocked it off several times. Actually I'm surprised the little clips that hood uses haven't broken.

All my EF lenses using bayonet mount hoods... no problem. In fact, I also have a number of old FD/FL Canon lenses and hoods with bayonet hoods... and all those still work fine too. Some of those bayonet mount, "click mount" hoods are a little difficult to install an remove... a tight fit that takes a little effort (I've even "lubed" one or two with a little candle wax rubbed on them, in the past).

I only mention my own experience because I find it a bit odd that you're having the same problem with hoods on two lenses... while many of use a lot of different lenses with similar design hoods without problems.

However, aside from that, what's working fine for me or anyone else doesn't solve your problem.

You might be able to add a dot of super glue to the lens or hood, where it's supposed to click into place, to make the fit tighter. I've heard of people doing that when lens and hood had seen a lot of use, so there was some wear and loosening of the latch.

Alternatively, you might be able to carefully use a hot, pointed tool (such as a wood burning/soldering iron... or just something pointed that's heated) to form a slightly more pronounced "bump" in the plastic where it's supposed to click in place. Don't overdo it, though.

You also might try carrying lens and camera differently somehow. The hood must be bumping your leg or something while carrying, to knock it loose.

FWIW, on more recent lenses Canon is using a new style bayonet hood that has a more secure latching mechanism. To release the hood, you have to press a button on the side of the hood. It works well, in my limited experience with it. Unfortunately, hoods with this new latch mechanism tend to cost more: $45 to $50 apiece for those needed for the EF 24mm f/2.8 IS USM, 35mm f/2 IS USM or a replacement for one like comes with the EF 100-400mm "II". (I've long thought Canon was cheap not including hoods with all their lenses... not just the L-series... the way they do.)

Lens hoods are important... protecting the lens both from oblique light and from inadvertent bumps. Hopefully you can solve the problem.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

The lens hood is my protection for the front element of my lenses. I never carry a camera on a strap.

Paul J. Svetlik Loc: Colorado

The best lenshood for any camera is a geared compendium.

Medium and large format camera makers make compendiums for their models that could be modified for smaller cameras.
The lightest one I like is the compendium made for Hasselblad cameras. Larger compendiums you can get from Lindahl, Ambico and some others.
For my back country hikes and climbs I made a stiff cordura fabric strip lined with a black velvet with Velcro closures at the ends - a sleeve, adjustable for different lens size.
It is very light and helps in some difficult light conditions, although, sometimes in a hurry, even the hat will have to do.
The butterfly hoods are usually good - just for the good look or lens protection.

When I need to use graduated neutral density filters the hood makes the operation difficult if not impossible.

DaveO Loc: Northeast CT

And also a few with no sense of humor! Life's too short...

jeep_daddy Loc: Prescott AZ

This is common with the "kit" lenses that Canon includes with a lot of the starter kits. These lenses are entry level lenses therefore they are not exactly going to have the fit and finish of a more expensive lens. Do the best you can with them until you grow out of them and decide to purchase a quality lens from Canon.

will47 Loc: Indianapolis, IN

I have had Canon all my life and never had this problem. But I can tell you this: when you put the hood on, and you think it is on, give it just one gentle little twist and you will be able to feel it click into place, and at times you can hear it. You always seem to think they are on correctly, but you don't do the last twist. I have done this.

Dennis833 Loc: Australia

The best advice I can give you is to always use your lens hoods on every lens and every shot.

dar_clicks Loc: Utah

I’ve done the masking tape to make the fit more snug for a hood that wasn’t designed to click — kinda works . . . for a while!
- Super glue should be avoided for anything on a camera. It can offgas enough to put a thin nasty coating on optics’ surfaces.

DaveO Loc: Northeast CT

I'll be really careful, super careful.

PatM Loc: Rocky Mount Mo.

What a novel idea Jerry. Me thinks I should present it to my wife. 😎🇺🇸

DaveO Loc: Northeast CT

Jerry always has valuable answers.

PatM Loc: Rocky Mount Mo.

Thank you all for the suggestions. Some are quite humorous. My temporary fix is to use Teflon plumbers tape. It seems to give a little more tightness to the connection. The white on Black is visible. I will try this for awhile. Thank you all at UHH

cytafex Loc: Clarksburg MA

When this happens to my lens hoods I place a drop of Super Glue on the lens hood (with it off the lens) where the prongs stick out and it restores the friction and stays on the lens.

GeorgeH Loc: Jonesboro, GA

I like the Teflon tape suggestion! My Pentax lenses use the bayonet hoods; eventually they wear enough so that they aren't "tight." A little paraffin wax seems to help a little in preventing the wear; any sort of grease would hold any grit. And of course replacement hoods aren't cheap! I am a firm believer in lens hoods; I've been amused at some shooters who ask me what is that funny looking thing on your lens?